The plans are sized and dimensioned to use nominal dimensioned lumber (such as 7 1/2 x 7 1/2).
The plans are sized and dimensioned to use nominal dimensioned lumber (such as 7 1/2 x 7 1/2). We design our frames so people can go to a typical lumber yard and pick up the material, all of which would come nominally. You can use the plan for both square rule or edge rule depending on your needs.
If you want to use true-sized timbers (such as actual 8x8s) you will have to make adjustments in the joinery. It might be easier to take your timbers to a sawmill and have them planed down to the sizes noted on the plans.