Definition (copied from doc)
The offset is added to the measured quantity before the UE evaluates whether an event has occurred. Improper use of non-default values may result in instability and unequal cell borders.
By applying a positive offset, the UE sends a MEASUREMENT REPORT message back to the SRNC as if the measured value is offset higher than reality. By applying a negative offset, the UE considers the measured value to be offset lower than reality at event evaluation.
-10 dB (late detection) –> 10 dB (early detection)