Tolerance on feeler gages?

[CannonBall]

My feeler gages are english units to the thousandth of an inch, they also go to the thousandth of a mm. One is .153mm; since the mercedes only specifies .15 does that include a +/- value? Are the tolerances on a feeler gage better than general rounding i.e. <5 go down 5 and greater go up? Would this be a bad assumption to make? Should I just go borrow metric gages from a friend? This is the first time I've done the valves on this mercedes, so some help would be nice. I've been letting the engine cool down since I had to drive it home but some intake feel pretty loose using the .153, I've been reading quite a bit about this, but some jargan might need explanation if you reply, thank you.
-Nate