Question about Boots Chemists (UK)?

Hey all, does anyone ever use the weighing/height machines at boots? I'm just wondering if anyone knows if they tend to be reliable or not. Because last time I used one, I was heavier than they actually said.

This time I've used a set of electronic scales that said I weigh 10 stone 5, whereas the boots ones said I weigh 10 stone 9... so bit confused :)