Replace Action on Grouping tag is not working for me

Hi all, Mixed in key is a music analyzer and tagging program that always seems to take useful stuff away on every update. I am a DJ and I only have about 3 characters space for MIK's Energy level on my controller. In MIK 8 they now force you to write "Energy" in front of every numerical value for the Group field (in 7 they didn't force that). So my Grouping tags always look like this:

"Energy 6"

I want to strip the "Energy " including that space at the end so it just shows the number. "6"

I have tried Action "Replace", Field "GROUP", Regular exp "Energy " and With "" <- empty

It dose not seem to do anything for me. I have tried a couple other ways but have not had any luck and now I am hoping you guys can have a look at what I am doing wrong.

Thanks for reading!

See here for a list of field names: (it's the help)

GROUP is none of them. Perhaps you look for ARTIST or ALBUMARTIST.
You also can check the correct field name in the extended tags dialogue (Alt-T).

As you intend to replace a string constant ("Energy") with another one (although it is an empty string), it is not necessary to use an action of the type "Replace with regular expression" but a simple "Replace" does just fine.

Awesome, thank you for the direction. Extended Tags showed that "CONTENTGROUP" is the field. I forgot the the column headers are nick names.

I greatly appreciate the direction! Thank you