> How are rows read and rows written calculated? > Every time a query retrieves a row from the database, it is counted as a row read. Every time a row is written to the database, it is counted as a row written.

From the billing docs:

> our paid Scaler plan comes with 25 GB storage, 100 billion row reads, and 50 million row writes

> Every row read from a table during execution adds to the rows read count, regardless of how many rows are returned.

> You can test a query for approximate rows read using the EXPLAIN statement. Running EXPLAIN with your query will return information about the query execution plan.

> To see the exact rows read, you will need to run the query. You can use the EXPLAIN ANALYZE statement to do this. It will return the estimated information about how it will run the query, run the query, and then return the actual impact from running the query.

> Another useful way to check rows read is using innodb_rows_read. This server status variable will show you the number of rows read across all tables. You can run it before and after queries to calculate how many rows were read.

These bits are extremely specific, down to the storage engine level. I don't know what more you could be looking for as to what "rows read" means than `innodb_rows_read`.