How to change font for Summary Visualization

[adam_mc]

CA 12.0.2

I am having trouble changing the font for the data value in a Summary visualization.

I can change the font for the "Header" text easily, but cannot locate how/where to change the font size for the
associated data value.
I have multiple summaries across the top of my dashboard and it appears as if it is using a proportional font size for each so as to take up as much space as possible within each visualization.
Unfortunately, this causes a ragged set of font sizes to be produced and I'd much rather have some consistency.

Any help would be greatly appreciated.
Thanks in advance,
Adam.