The number of decimal places displayed for Mu and Var values in regression tree graphs is 6 by default. 
How to adjust the decimal places for Mu and Var values in Regression Tree graphs?

This article provides alternative solution for use to adjust the decimal places for "Mu" and "Var" values displayed in regression tree graphs.

Windows 7， Windows Server 2012 R2

After the regression tree graph is generated in a workbook or reporting document node in workspace, 
RESOLUTION 1:
Right click on the graph and select "Graph Options" from the dropdown menu to open the graph options dialog. Under "Graph | Titles/text" tab, user can find the list of all the texts displayed in the tree graph. User can select the text of interest and manually edit the decimal places in the editing text box. 

This method requests user to edit the Mu and Var values one by one, and therefore is inefficient if the tree is big. 

RESOLUTION 2:
This workaround proposes a SVB macro to adjust the decimal places for all the Mu and Var values in the tree graph. The SVB macro is attached in this article (AdjustDecimalPlaces_RegrTreeGraph.svb).
Click on the tree graph from the workbook or reporting document node to make it active, open the attached SVB macro, edit the CONST_iNumDP value to be the number of decimal places you want to set, then Run the macro. The Mu and Var values in the tree graph will be automatically adjusted to have the specified number of decimal places displayed.