Perhaps this one : GCH_RED_FACTOR_High_Ater_Usage
The GCH reduction factor applies to the new PDCHs which are used when the Ater usage is “high”.
In other words, when Ater is “high” loaded (above Ater_Usage_Threshold %) then a PDCH can only get 75% of the GCH it requires to transmit at full throughput.
1 PDCH usually requires 4.5 GCH (to be able to get MCS9). In case of Ater hi-load, then it will only get 3.375 GCH (which should give a allow MCS 6 max, I guess ?)