Wtf,BofA site says balance for CC is higher than it's listed somewhere else

On the Bank of America page I go to my credit card page and look account details top left and it shows it is $300 which is higher than it is listed in the transaction history. In the transaction history page it shows my transactions and on the right it shows balance which is $270. I checked to see if there was any error or if I just recently bought anything which I did but the thing I recently bought was already added to my balance. Is this **** some hidden fee or something that isn't on the transaction list? I payed off the3 $270 and I refuse to give the $30 just for the hell of giving out free money. I would call the bank but they're closed right now.