Why is there a large "Unused RIs" cost at the first of each month?

Products

• CloudHealth

Issue/Introduction

At the beginning of the month, it is expected there will be a large chunk of Unused RI as this is what needs to get used over the course of the month.  

• You may notice a spike in Unused RIs at the beginning of each month. 

• However, day-by-day as the RIs are being consumed you will notice this cost decrease as your Compute charges increase.

 

For more details here are 2 useful links:

What are 'EC2 - Unused RI' costs? 
How does the Amortization cost report work?