AT2 is generally not required. I am not sure about your business needs. But, check in CIN configuration under Basis settings-Excise registrations check the option Liable for AT2 is checked. If its checked then go to path Specify Excise Accounts per Excise Transaction and check whether the RG23A2 is assigned against the transaction type. If assigned, go to path Specify G/L Accounts per Excise Transaction and ensure GL is maintained.
Could you confirm in which field you have entered the RG23AT2 amount in J1IS?