Hi,
@velofan , a lot of it is to do with the way meters work.
They're not like precision weighing scales, where you would expect the result to be the same.
The strip contains an enzyme, typically glucose oxidase, although there are others, which oxidizes glucose in the blood, breaking it down into hydrogen peroxide and a few other things, the chemical reaction gives off electrons, the meter measures those as an electric current - the higher the glucose, the higher the current - and then decides what that amount of current represents as bg.
There's a lot of flittery "guesstimation" going on in that situation, so it's best to regard any reading as a "ballpark" figure.
Your readings are all in the same general ballpark, so, even though they are different, you've got some reassurance they are all about 5 and not 3 or 8.
I'm T1, inject insulin, so numbers are quite important to me as they are the basis of dosing decisions, but I learned long ago, from having to visually assess colours on a bg strip against a chart on the side of the strip container that numbers after the decimal point don't matter.
Other reasons for the differences are that bg levels naturally move around all the time as it is not a static system, and even in a short spell of time, there is no reason why concentration of glucose will be evenly distributed around the body.