Parameter description for ESS job "Validate and update cost accounting periods" unclear in 23C notes

I have opted in the new feature released in 23C for cost accounting period close "Validate and update cost accounting periods". As part of this, when running the ESS job, i see that there are two new parameters where more clarification is required after reviewing the 23C release notes. Please help me to understand the same.

1. "Date to Derive Accounting period" - What date needs to be given here? is it the last date of the to be closed accounting period or the date for newly opened accounting period? From the 23C release notes it is not clear.

2. Number of worker processes - What does this mean? it is not mentioned in 23C release notes.