You will probably find that your zone is not actually exactly 7.242 x 10.673
It may well be 7.2418 x 10.6726 which will round to the dimensions you have shown.
But the calculation will be based on the real figures - total = 77.28883468
which will round to 77.289
So I would say it actually is correct but you are not displaying the full decimal precision to which it has been drawn.
Barry.
One of the forum moderators.
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