Zluri gives you two metrics to monitor cost for any contract. 

Cost: Obtained from the contract value

Spend: Obtained from the actual transactions. 

Let's say a 12 month contract is starting from 01-Jan-2022 uptill 31-Dec-2022 for 100 users at a cost of $3 per user. The cost for the month of January gets calculated as $300. Now let's say there are additional 20 users for which license is purchased in the month of March. Cost for the month of March is calculated as $60. Similarly if there are 30 more users added in the month of September, The cost for September is calculated as $90. 

The spend is not calculated as such. It is the actual spend for the particular app as recorded in the transaction csv or financial systems.