docs: Clarify rows meaning

Author: paveltiunov

docs/content/Deployment/Production-Checklist.mdx

@@ -133,7 +133,10 @@ requests per second. Every Core Cube Store router node can serve 50-100 queries
 per second. As a rule of thumb, you should provision 1 Cube Store worker node
 per one Cube Store partition or 1M of rows scanned in a query. For example if
 your queries scan 16M of rows per query, you should have at least 16 Cube Store
-worker nodes provisioned. `EXPLAIN ANALYZE` can be used to see partitions
+worker nodes provisioned. 
+Please note that the number of raw data rows doesn't usually equal the number of rows in pre-aggregation.
+At the same time, queries don't usually scan all the data in pre-aggregations, as Cube Store uses partition pruning to optimize queries.
+`EXPLAIN ANALYZE` can be used to see scanned partitions
 involved in a Cube Store query. Cube Cloud ballpark performance numbers can
 differ as it has different Cube runtime.