It shouldn’t do - they’re loosely typed in that sense. To confirm, the values you are checking in the debugger are under Global Variables, and not Scene Variables?
[edit]
If the values are correct, is there anywhere else in your events you changing the width of the health bar object?
No, the “strict typing” only means that the IDE doesn’t guess the type of your variables but needs to know the type when editing them, at runtime the variables can still change types without problems.
(Regardless, if the variable is a number I would recommend storing it as such not as a string :p)
100% sure they’re global values, and nothing else is messing with those values as far as I know. (Sorry for late reply, forums decided I reached my reply limit)
To follow up on what @Silver-Streak just wrote, if setting the width using that expression works, then check the variable names are correct. It’s case sensitive, and any spaces before or after the name will be considered a mismatch.