Hi Nathan. Unfortunately, as of right now there is no way to change the format of numerical data when viewing a decision tree in graph mode. Our development team has been notified of this as a possible enhancement, and will look into it for future releases.
Workaround: save the graph as an SVG file, then edit the SVG code. To declutter the graph you can remove all of the left branch text (<), which is grouped in one section of the SVG file, since the right branch text (>=) is sufficient.