Your Input Tax credit has only CGST and SGST (as you don't have any interstate purchases)
But your tax payable has IGST (as you have interstate sales) and may also include CGST and SGST if you have any local sales
So while paying tax your order of set off will be as follows
Paying IGST - Can be paid from CGST and SGST
Paying CGST - Can be paid from CGST
Paying SGST - Can be paid from SGST
and remaining credit should be paid in cash.
you can first pay either IGST or CGST or SGST from the input credit available and remaining should be paid in cash. There is no prescribed order.
order of set off prescribed only for input credit setoff. This will be applicable to you only if you have IGST, CGST and SGST input credit.