I’ve got a 42 year game on the current (1.4.4) Steam Windows version of GDT, and my end game score crosses the 99,999,999 mark. It simply rolls-over like the odometer on your car and tells me my score is 10633460. The high score board lists it correctly as 106,334,603.
You went too far… 
Thanks for the feedback, we are aware of this.