Calculate subscription's lumpsum amount for monthly billing plan

[Slowman123]

How to calculate subscription lumpsum amount from last success transaction date to latest billing date for monthly billing cycle?

Note: 
Billing type: monthly cycle.

Example 1 : If subscription start on 31 Oct 2021 and Subscription suspended on 28 Feb 2022.
We need to calculate lumpsum amount from 28 Feb 2022 to till latest billing date.

Example 2 : If subscription start on 31 July 2021 and Subscription suspended on 30 Apr 2022.
We need to calculate lumpsum amount from 30 Apr 2022 to till latest billing date.

[rslasad]

There are a few things you need to know in order to calculate a subscription's lumpsum amount for monthly billing: the subscription's length, the price per month, and any applicable discounts. Once you have that information, you can calculate the lump sum amount by multiplying the length of the subscription by the price per month, and then subtracting any applicable discounts.