ArcGIS Pro underlining issue with Annotations

[MarkSenne]

I'm having issues with label formatting with annotations in ArcGIS Pro. The label doesn't seem to register the additional spaces at the end of the label. So for example my labeling script is as follows:
<FNT style="Bold">KB-2030-SS07
</FNT><UND>ANALYTE 0-0.5' 0.5-2' 2-3'     
</UND>PFOS 494 ab 1030 ab 222 ab/245 ab

but my issue is that I want the under line to go all the way to the end of the results (see examples), has anyone had success with this?

Bad label.jpg = how the label format looks even though I have extra spaces after the 2-3' in the label script (ArcMap would register these extra spaces but ArcGIS Pro clearly isn't, unless I'm missing something)

Good label.jpg = how I want the label to appear (drew in red underline to show what I want) manually drawing in underlines for each label just isn't feasible practice when there are potentially 50+ labels on the map

[MErikReedAugusta]

The first thing I'd check is whether those spaces are actually printing in the label.  In the Label Class pane, there's a checkbox to remove extra spaces.  Make sure it's unchecked, and see if you're still having this problem.

That said, the better way to fix this is likely by using PART formatting tags, and a composite callout:

You should be able to set things up so that the line that you're currently trying to underline goes in the MIDDLE part, and then put a line at the bottom of the part, if memory serves.  The only thing I'm not sure of is how that will interact with your current whole-label border.  Might take some tinkering to get what you want.