problem with quotation of parts with fitting

[enpa28]

Hello everyone, for the first time I'm approaching drafting.
I would like to quote that side that in the first photo has size 7 mm, but having connected the surfaces, the quota turns out to be 6.82mm (see the photos); I can't quote by taking the connecting centers as reference extremes.
thank you all for the answers!

 

[dandao]

when quoti activates the intersection point command that black point on the tool palette bar and will quote you 7

Hi.

Daniele

 

[falonef]

opuure uses automatic quotation even if this function does not excite me