This number reflects the rate at which users are executing a stored procedure. The rate reflects executions where the needed stored procedure was in cache (cache hit) and those where a read from disk was required (cache miss).
As users execute stored procedures, Adaptive Server looks in the procedure cache for a query plan to use. If a query plan is available, execution begins.
If no plan is in memory, or if all copies are in use, the query tree for the procedure is read from disk and is a procedure cache miss.