Are you looking for more than 3 decimals on the interaction ratio? That seems like overkill. Maybe you are looking for fewer significant digits due to screen clutter. In that case you might want to use color ranges with no text on screen instead.
If you are trying to focus on members with a certain range of interaction ratios, this tech note is useful:
I want to reduce the number of decimal points to 2. At the moment 4 or 3 seems to be an unchangeable default and I would like the diagram to show the utilisation ratio.
I know that I can't change the VALUE of the utilisation, I merely want to set the number of decimal points to 2 in the diagram to make it more legible.