Last week my chainset was replaced (in warranty) and I just found out that the chainset is 10 speed (FSA Vero) but my rear cassette (+Claris gears and shifters) is 8 speed.
I want to know if I will be fine. The bike is Carerra TDF Limited Edition 2012 model.
In my experience this is a non-issue. The only difference between 8,9,10 speed chains is the exterior width not the interior. That matters a lot on the rear cassette, but not much if at all on the front. From this article the difference in the exterior width of 8spd chain vs 10 spd is 0.9mm. On the front that just doesn't make any signficant difference.
If you had a triple crankset and really short chainstays, you might run into some issues, but with a double and your bike, it should just work.
I'd say take the bike for a test ride and if you're happy with the way the front derailler shifts and it is capable of cross-chaining then I wouldn't worry about it. At this point insisting on an 8spd replacement will only get you a very low quality crankset.
The distinction of speeds especially in the front is primarily for marketing. You're fine with this '10 speed crankset'.
Mostly, the different designations are there to encourage whole component group sales. As a general rule (not an absolute one), you can mix and match derailleurs and chainrings with other parts, but only with a one speed difference and with the other parts being the lesser speed.
In other words, 8 speed chain, shifter, and cassette (these three must match except for 6-8 speeds) are ok with 9 speed elsewhere, but not 10.
Realize that there is usually a difference in chain width, so there are potential exceptions to this rule.
