What does the man mean when he says this:

[Professor (female)] Q7 Class, I have a question for you. What’s a sugar bush?
[Student A (male)] A sugar bush? isn’t that a species of bush that you can get, um, sugar water out
   of? For making syrup?
[Student B (male)] No, no...it’s not a bush. A sugar bush is a, a grove of maple trees, and those trees
   are used to produce the maple syrup.
[Professor] You got it. Q6 And that’s what I want to talk to you about today: maple syrup
   production. Now, some of you are probably really familiar with the process.
   Especially if you’re from somewhere like Quebec or Vermont...or anywhere
   else in northeastern North America. ’Cause that’s a center for maple syrup
   production. Canada makes the vast majority of the world’s maple syrup: 80%.
   Vermont is the largest producer in the United States, followed by Maine and
   New York. But even if you don’t live in the Northeast, you still might’ve had
   the opportunity to see maple syrup being made, because it can basically be
   produced wherever maple trees grow.
[Student A] But are some types of maple trees better for making syrup than others? There
   are lots of types of maple trees, aren’t there?
[Professor] Yes. That’s a good point. Most of the time, maple syrup is made from sugar
   maples or black maples--since their sap has a pretty high sugar content. About
   2%. Sap--you know what that is, right? It’s the fluid that runs through the
   vascular system of plants. It’s a mixture of sugar, water, salts, and minerals. And
   it’s the raw form of maple syrup.
   So how does the process work? Well, maple syrup production usually happens
   in early spring.This could be February, March, or April, depending on the region
   and the weather conditions. Q9(A) Basically, you need to have nights where
   the temperature drops to below freezing and then days that are pretty warm.
   Conditions like these cause the sap in maple trees to start running. When the
   temperature drops below freezing, water gets taken in from the soil.Then when
   the temperature rises above freezing, the sap starts to flow. So when maple
   syrup producers drill a hole in the trunk of a maple tree, the sap will run right
   out of it. It usually flows for a period of about, um, 4 to 6 weeks.
   I already mentioned which species of maple trees are best to tap, but there’re
   other considerations as well. Experts look for trees that are, um, out in the open.
   Trees that don’t have to deal with a lot of competition from other trees nearby.
   These kinds of trees produce a lot more sap than trees that grow in crowded
   forests. Um, for example, 15 to 20 gallons of sap in a season compared to just
   10 gallons a season for forest-grown trees.
   Once the trees have been selected, there’s some setting up that has to be done.
   Q8 It really only takes some basic equipment like Q8(A) a bucket for collecting
   the sap and Q8(B) a spout for directing it as it runs out of the tree. Of course,
   larger operations use more sophisticated equipment like, um, plastic tubing
   and pipelines to make the process more efficient. But the basic idea doesn’t
   change.You drill a hole in the trunk of the tree, insert the spout, and position the
   container to collect the sap as it runs out. Oh, and if you’re doing this year after
   year, it’s important to remember that you have to drill a new hole every time...
   cause each hole is good for just one year.
[Student A] Q10 But didn’t you say that the tree sap is only 20% sugar?
   I don’t know how much sugar is in maple syrup, but I know it’s more than that!
   How do you turn sap into syrup?
[Professor] Well, after collecting the sap, you have to process it to get the-product we’d
   recognize as maple syrup. And this is pretty simple too. All you do is boil the
   sap down for a long time until it gets really concentrated.
[Student B] Hmm...so it sounds like you end up with a smaller amount of syrup than you
   had of sap, right?
[Professor] Yes. Q11 Actually, it takes forty gallons of sap to make just one
   gallon of syrup, if you can believe that.
[Student B] [in disbelief] Forty gallons?
[Professor] Uh-huh. Well, it depends to some extent on the sugar content of the sap
   you start with. It can vary between about 20 and 60 gallons. Q9(D) And...this
   processing of maple syrup, it usually takes place in a special building called a
   sugar house. See, since so much steam is produced while the sap boils down,
   processing it anywhere else could cause damage to the walls of the structure.
   Sugar houses are designed to deal with and vent all that steam. When the sap
   boils down to a concentration of about 66% to 67% sugar, you’re done. All you
   do then is filter it, and then it’s ready for use on pancakes and waffles.