Yes they do line up
DD.DDDDD is degrees/decimal degrees
DD MM.MMMM is degrees/minutes/decimal minutes
DD MM SS is degrees/minutes/seconds and sometimes decimal seconds at the end of seconds.
The Google numbers you stated are the last of those three. There can't be more than 60 minutes or 60 seconds using that format.
31 Degrees 12 Minutes 46.94 Seconds is the first one
The Humminbird numbers are Degrees/Minutes.decimal minutes
31 Degrees 12.782 Minutes
If you convert the GE format to Degrees/Decimal Degrees----DD.DDDDD
that would be 31.21304 and that lines up too.http://www.gpscoordinates.eu/convert-gps-coordinates.php