As per the terms, it should be applied on the total bill.
What do you mean by fuel transaction requirement?
Monthly milestone tnc states
3) All spends are considered except: • Wallet loads/payments (MCC 6540) • EMI transactions • From 5 th March, 2023, Rental Payments/Transactions (MCC 6513) will not be considered for Milestone benefit. • Transactions which are reversed/cancelled/refunded • Cash withdrawals
And as per confirmation from cust care, fuel transaction will be included in the milestone spends. There seems to be no additional terms for fuel transactions.