I work in a nulcear pharmacy and we use 110s, to frisk out of the lab we use a 110 probe and a wall mounted foot monitor that are both attached to a common exit meter, and we use a energy compensation probe used to detect beta/gamma (it is an 8 inch aluminum probe with a nob at the top you turn to open a window in the side of it.) The source for each instrument is attached to the side of the meter, we are basically doing a response check. Each morning I check the instrument and write down what the reading is. An example would be, I get 12,000 cpm one morning, but maybe the next it is 14,000 cpm. I would take into account that there may be a change in background or weather or geometry of probe, etc.
I know this is common when you are dealing with a weak source to get some variations, but when we are told that is impossible and to only write down what the sticker says, well I had to clear my throat. Im needing some clarification just for my own peace of mind. Being a former Radcon we always saw slight variations in readings that were within an acceptable range, and thought nothing of it.