That 100hz i think is a feature in that tv that is called Auto Motion, here is some info on that.
120 Hz Motion Plus technology estimates and inserts an extra frame between frames to create a more comfortable viewing experience. The extra frame makes images appear seamless to your eyes, and eliminates the motion judder and image bluming that can occur when watching movies and sports. Even the fastest action scenes are presented with precision and clarity on the SAMSUNG LCD TV SERIES 6 650 (Applicable to over 40" model).
The tv should still work for the 60hz as that is more like a region thing, like NTSC = 60hz and PAL = 50hz, but i think that 100hz is for the frame in between frames only i think, not 100% on this but it does seem like that might be what that is for only.