This isn't really in the right section. I notice that you are new to EpicSki, so welcome! There are lots of sub-sections in teh forum and you are more likely to get a useful reply if you post in the appropriate section.
Presumably your shop has a device for measuring the force required for releasing the boot from the binding. Both this device and the binding setting screw on your skis will have some innaccuracies. Whenever you measure or set up something using two different systems you will find that they only agree to a certain level of precision. This is due to manufacturing tolerances, difficulty in reading to high precision, random effects etc.
The questions are:
a) whether you believe the measuring device the shop has is more believable and accurate than the binding setting indicators on your skis
b) whether plius/minus one DIN setting is that critical. DIN 5-6 is a fairly low setting. Unless you are very small and light, I don't think it's a major issue. What do you weigh? How aggressive do you ski? Since they have set the skis lower than 6 (which seems to be what you want given you weight), the outcome might be a prerelease. This is not usually as bad as a binding which doesn't release in a fall, uunlöess you are doing really extreme skiing where a pre-release can be a serious matter. But then you would have your bindings at a lot more than 6....
I am a bit suspicious that the differences are not consistent. If there was a consistent difference (for exaple with both back bindings set lower than expected). So I would wonder how accurate their measurements were.
It's not a big deal.