DAX ALLEXCEPT vs ALL & VALUES

Workbook attached.


Hi,
Generally in measures I have used ALL and VALUES rather than ALLECEPT, but i've been trying to use RANKX as a calculated column ;


and have this; ;

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Which seems to give the correct answer.

but is this case if I replace except with

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it no longer works? I just get a 1 for each 'row'. Why? and are there better ways of achieving this

I evenutally wanted to use this in a running total

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But I'd like to understand why the All and Values does not seem to work.

Richard.