How to increase the dimming range of mosfet controlled LED
How are you converting 0-100 to 0-255?  It looks like you're using the external map function.  All would be explained if the map function were "malfunctioning" and returning 155-255 for a 0-100 input.  Since 155 is 60% of 255.  Perhaps that function does not work the way you think it works. 

Why not simply go t = intR * 255 / 100? 

For that matter, why even input a 0-100 scale, think in binary and input a 0-255 scale.