Intimattion under u/s143(1)(a) payment head of account

I have received an intimation u/s143(1)(a) regarding inconstitencies between ITR and Form 26AS.I agree to the assessment and propose to remit the  amount.Please clarify  the account head for payment whether it is 0021-300(self assessme nt)or 0021-400(Regular Assessment).

Pl. also clarify whether I can submit a revised return after payment and then "Agree" to the intimation to avoid any possible delay.