Why is the "Bet Pot" amount larger than what appears to be in the pot?

[crystalallen]

I have recently decided to try playing poker for money so I signed up at UB. This is my first time playing with a "Bet Pot" button. It's really throwing me off.

An example: I'm first to act, 20 and 40 blinds are posted. I look at the Bet Pot button and it says 140. ???

Where does this number come from? And is this the number you use for pot odds calculations?

Thanks!