If you were trying to top off the refrigerant by adding refrigerant to the system under these conditions to get the high side pressure higher, so it would not drop down below what somebody may have told you.
For example, if somebody told you that the high side pressure should be 175 psi. But the computer and cycling the fan keeps dropping the high side pressure down to around 100 psi and you keep adding refrigerant to the pressure no longer drops down to 100 psi you would be overcharged.