Both Excellon and Gerber files are variants of RS-274, commonly called "G Code". But, one of them suppresses the leading zeros, the other suppresses the trailing zeros. In both cases, the decimal point is suppressed. There is a format specifier line that begins "FSLAX" and tells what the format is for the X coordinates, then after the Y it describes the Y format.It is most likely that Seeed's software didn't recognize your format specifier.
There are various CAD/CAM packages that are meant to check Gerber and drill files. Also, cad packages have various options to set number of digits to send in the files, and where the origin is to be. I use Protel 99, and have to always set "use relative board origin" or the Gerbers and drill file do not have a common origin.
Jon