Strange Gerber Statement
The "D" indicates a decimal coordinate format rather than the integer format assumed by the alleged specification you linked to, which seems not to cover all features in the, shall we say "living language".  

What your board house can support is between you and them; if there's an issue first recourse would be trying options in the output menu to get an integer format, next would be reprocessing the data with your favorite string-processing language (even sed would probably do).  In either case you probably want to do some manual verification that the interpretation is as expected the first time around.

For example, here's a few lines snipped excerpted from a file I found with a google search for occurrences of your format string (source http://homecinepc.free.fr/bassm/serigraphie.ge4)

%FSDAX23Y23*%

X20.31Y34.3D02*
X22.85Y34.3D01*


For comparison, here's some lines from an "integer" gerber from an old project of mine:

%FSLAX24Y24*%

X006851Y007351D03*
X006851Y006351D03*