Hello Pradyumna
This particular command combines the track instance configured in the static route, with the IP SLA instance. The first number (track 1) refers to the track number used in the static route. The second number (rtr 1) refers to the IP SLA instance.
This lesson is relatively old and the syntax used has changed since IOS 12.2(33). Rene will be updating this soon, but you can see the newer syntax at the following link:
And here is some information from the relevant Cisco command reference as well.
I hope this has been helpful!
Laz