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A lot of it is that they don't look right together, rather than awful per se, but the 6 and 8 are pretty awful, for example. See how small the 8 looks compared to the 2. The 9, 8, 6 and 3 are too similar to each other. But especially, check the 2 - when you use an outer radius that is the same or smaller than the internal radius, what you get is a stroke (line) that gets thicker in the middle of the curve. So you get blobs at the corners, and on the 2 you get it at middle left where it curves down to the bottom left corner. The left side of the 2 looks heavier than the right side.
They've generally not compensated for the rounded corners so where there's a sharp corner, the numeral looks much bigger - the top of the 5 looks wider than the curved bottom, which is the opposite of what you'd normally see in a 5. Obviously, that's the idea, the conceit, but it doesn't make for very nice numbers (IMHO as always).
I like what they're going for but not the execution. The way it's been done is quite amateurish/student-y IMHO - someone has had an idea ("circle within a rounded square") and slavishly stuck to the rules they made about what curve goes where, even though it makes things look weird/inconsistent/wrong. It looks good on some numbers and awful on others.
Shame, because the case and dial colour/ texture look great, and Hermès are usually pretty good with this stuff.