Usage is measured in Data Units, which are consumed for every record (or row) in the data you upload/add to Kapiche.
When you add data to Kapiche, every record (or row) in the data that is added to a Project consumes one Data Unit.
1 Data Unit = 1 row of data from a spreadsheet or integration
In other words, if you were to upload a .csv with 5,000 rows of data to your Project, you would need 5,000 Data Units. Another example would be if you were to use an integration to import 10,000 respondants, it would use 10,000 Data Units.
Data Units are allocated based on your Site's plan.