Promotional cash discount

I am small shopkeeper with a basic knowledge of accounts. I maintain my accounts business books.

I started using AJIO business recently. It offers promotional cash discount in every transaction. Such discount is not mentioned in invoice.

Moreover AJIO bill  amount can be divided in 2 parts - 20% of the order amount has to be paid in advance and the remaining balance has to be paid later.

1.  what would be the entries of promotional cash in books of accounts? 
2.  could I do entry of Advance payment and balance collectively 
3. Instead of writing each discount entry individually, Could I write promotional cash / discount received from all the transactions collectively of each month? As advance and balance amounts of 2-3 bills are sent collectively

For example I am posting a copy of one online receipt

Total Payable Amount : ₹13,651.36
Payment Term : Pay Before Delivery

Total Advance
₹2,730.27
Advance Paid :
₹2,730.27
       Promotional Cash :
₹273.03
       Cash :
₹2,457.24
Advance Pending :
₹0.00

Total Balance
₹10,921.09
Balance Paid :
₹10,921.09
       Promotional Cash :
₹1,092.11
       ONLINE :
₹9,828.98