Remaining budget does not tally

[Dominic Lim]

Steps to reproduce:

Starts up app for the first time

budget a/100
add d/test a/10 t/2022-04-16
budget a/5

Expected:

Maybe some validation on the remaining amount left for budget. Does not tally with current expense in list.

Actual:

[nus-se-bot]

Your response not required for this bug as the team has accepted the bug as it is.