Apple Card pay more than previous months balance.

I like to round up my payment to an even number. If I try to set up a future payment that is larger than the previous months balance, the pay later button dims. It will let me pay it now, but not set up the payment for the due date. For instance, if last months balance is $893. Current balance is $1200.00 and I try to enter a payment of $900 by the keyboard as soon as the last zero is put in, the pay later button dims, but the pay now button is still active. If I stop at $90 I can pay later or pay now.