Hello from Japan!!

[Grumpy Goat]

Not saying that you are incorrect and that the pads you received are not improperly dimensioned, but the way you are holding it in the picture does not allow the pad to follow the hollow curvature of the tank, so the top to bottom dimension could appear to be too long. If the pad is pressed to the tank and into the curvature, is it still too long?

Suggestion: apply several pieces of scotch tape doubled back on itself to form double-sided tape to the back of the pad, including across at mid-height and then fit to the tank and check for proper dimension then. Could even take a good picture of that test fit for the return process, if needed.