It’s saying if you have too low a travel wallet balance, it will pull from the debit side as a cash fare instead of a Key fare.

Tomorrow try to call in and say you mistakenly loaded it as travel wallet, and intended to load debit. Maybe there can move it or refund it.

Unfortunately I suspect the limit is there to prevent people from arbitraging pretax or reduced fares into a more liquid debit balance, so they may not be flexible on it.

And for the future, research your options for prepaid debit accounts. I don’t know that much about them, but septa key appears to be worse for fees.