It should describe the duties for the period now proposed, not the ones drafted for the original start, and state the profession using the Appendix 2 wording. Naming the equipment, the design responsibilities and the supervisor, with the revised dates and salary, keeps the letter consistent with what the applicant will actually do.
A stale letter is a contradiction waiting to be found
Support letters are usually written once and then quietly reused as the project timetable moves. That habit creates a document describing a January commissioning of a line that will now start in the autumn, alongside duties nobody expects Oluwaseun to perform any more. Reissue rather than patch.
The current version should give the U.S. entity's legal name, his full name and Canadian citizenship, the profession as Appendix 2 states it, and concrete engineering tasks: structural modifications for the new line, foundation and mezzanine design, drawings sealed for permit, review of vendor submittals. State the revised start date, the period requested up to three years, the salary and the reporting line.
Attach the parchment, the transcript and the provincial licence. Where an earlier version was already presented at a border, keep it, because inconsistency noticed later is harder to explain than a documented change.