Lets say you are at 1300lbs in a R22HP, you can operate IGE up to 8500’ PA in standard atmosphere and OGE up to 6,500’ PA in standard atmosphere.
To operate at OGE at 8,500 in the same conditions, you would need to reduce your AUM by 100 lbs.
So if you are at 1200 lbs you can operate at 8,500 but you still only just have OGE.
If you now reduce your AUM further by 5% (60lbs) or 10% (120lbs) of that OGE AUM, you have a thrust margin which will get you out of trouble and allow you to manouevre OGE with some degree of safety.
All this assumes you are at or under your max MAP in the hover.
It might be academic since the POH shows you can't get much more than 6,000 PA ISA standard at the limiting MAP.