Well the most important question is if you are under a food safety standard and what your document control policy, if you have one, says in relation to when you have to change a forms revision number.
The difference between what you perceive and what your manager is telling you is that in one instance you have a blank that is filled in like any other document and in the other instance you are physically changing the information printed on the form.
Depending on your policies and governing standard, if any, you may (or may not) need to change the revision number for the document.
I've worked in places where minor changes that weren't structural to what the document was for didn't require a revision number change and where I work now if you fix a typo or a misspelling a whole new revision number is issued. There is no hard fast rule on this... however if your document control policy says that any time a document is changed a new revision must be issued then your hands are tied.
My suggestion is to just put a blank there and have the auditor write in the week number. This way it only has to be changed once and your done.
-OR-
you could also put in a number circle system:
Indicate the week by circling the first (top) and last (bottom) numbers
0 1 2 3 4 5 6 7 8 9
0 1 2 3 4 5 6 7 8 9
I don't suggest this... but it is also another option.
Good luck and please as if you have any questions about what I wrote.