Well my friends guess What? Food labels aren't always accurate: Food Calorie Counts Are Frequently Off.
I know. I was SHOCKED too! OK maybe not.
If calories are off, can carbs be far behind? I think not. So there is a margin of error from the label and there is a 'range' of accuracy on the meter. YDMV.
At least there is a wide range of things to blame for random strange numbers.
I think it is the Brits fault. If nothing else blaming them is a time honored tradition here in the Colonies.