Hi,
To the best of my knowledge, it is not possible to change the format of these predefined GraphBuilder annotations. Hence, when confronted with this type of challenge, I use JSL to extract the desired parameter from the Fit Y by X > Fit Line platform, format the numbers as I see fit, and add the resulting text to the plot frame using the Add Graphics Script command.
This approach is worth the effort only if you have multiple plots to annotate; otherwise, I use the old-school method of annotating the plot manually via the Customize function.
Let us know if you are up for some coding.
Best,
TS
Thierry R. Sornasse