Infix declaration: digit or integer?

Hello Haskell-Prime, I just discovered that the Haskell 2010 report allows the precedence of infix declarations to be an integer instead of just a digit. Therefore, also the following declarations are allowed: -- compiles infix 0x7 <$> infix 0o7 <$> -- does not compile because of precedence out of range infix 0xa <$> infix 0oa <$> infix 123 <$> Interestingly, the in section 4.4.2 (Fixity Declarations) the report says:

The *integer* in a fixity declaration must be in the range 0 to 9.

as well as

If the *digit* is omitted, level 9 is assumed.

This is of course no problem, I'm just curious if there is some motivation for integer I'm not aware of. Kind Regards, Björn