I am not sure about this, but is it the Working Units?
Calculation Units control lengths, heights, widths in the schedule, but as you are using expressions, these oddly are not classified as calculation units.
In Working Units there is an option for 'Numbers without units' which might include expression results.
But as I say I am not sure, but might be worth a try.
Of course the expression will have to be a number and not converted to a string.
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