Would you be able to attach the report with saved data please?
To attach the report, change its extension to .txt first and then click on the "Use advanced editor" link in the reply window.
Also, you said the the number of machines (which is the Main group) for both the Main Report and the Subreport are the same. In the Subreport are the hours being calculated and displayed on the Group #1?
-Abhilash