How Many BPT in veBAL?
Are you trying value or determine underlying assets that are locked in veBAL? You'll need to query a few things from the veBAL contract. Most notably:
underlyingBpt = veBAL.token();
(amount, end) = veBAL.locked();
Warning
Don't use balanceOf on the veBAL contract if you're trying to calculate value associated with underlying tokens. balanceOf returns a time dependent value only useful for querying a user's current voting power.
Now that you have the underlyingBpt address and the amount of those BPT that you have locked, you can now analyze, value, or determine underlying tokens.