Both are external diameters. Wall thickness of 15mm is 0.7mm so internal diameter is (15 - (0.7 x 2 )) = 13.6mm. Wall thickness of 22mm is 0.9mm so internal diameter is 20.2mm. The above applies to standard half hard copper tube used in normal plumbing.
The imperial system pipe sizes referred to the internal diameter, so 1/2" pipe had an internal diameter of 12.7mm and 3/4" pipe internal diameter was 19.05 mm.
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