Historical Upgrade new Reporting Ledger to existing Primary Ledger

I am looking into adding a EUR Reporting Currency to an existing Primary Ledger in CAD. Per the documentation, I should initiate account balances first (Reporting Currency - Create Opening Balance Journals in Reporting Currency program) and then I can run the SLA Secondary/ALC Ledger Historic Upgrade Program to create journals.
Should the First Historical Conversion Period from the "Create Opening Balance" program and the Upgrade Start Period ofr the Historical Upgrade Program be in sync? How does the Uprgrade Program and the created journal impact the historical period end balances created by the "Create Opning Balance Journal" program?