uuid.md says:

        00. ?decimal index (up to 9999999999%, also 2D indices 4%5)

This needs clarification. Due to the rules for compression, 4%5 should be the same as 4000000000%5000000000, which is unexpected 😄 The 2D index (4,5) would be represented as 0000000004%0000000005, right?

It seems number UUIDs are currently unused, so the impact is low.