It appears that the Card is running with at least 1 VL-1 sleeper, and the 2nd "sleeper" is either another VL-1 sleeper or a VL-2 bag/dorm. So the question is not the difference between a VL-1 sleeper and a VL-2 sleeper, but between a VL-1 sleeper and a bag/dorm (all bag/dorms are VL-2).
The bag/dorm has only 9 Roomettes, and people have said that 3 of them are reserved for crew, leaving a maximum of 6 for public sale. I don't know whether the agents have the ability to identify that a car is a bag/dorm.
But here's good news: the consensus is that, if there is a bag-dorm, it has a line number ending in "09", so 5009 or 5109. The first VL-1 sleeper has a line number ending in "00". I don't know whether a 2nd VL-1 sleeper in place of the bag/dorm would still end in "09", or something else (most likely "01" or "10".)
ETA: corrected VL-1 sleeper line number to end in "00".