Sometimes TThrottle detects more cores than there actually are.
The Intel I7 processor reports 8 cores (when HT is active) but it has "only" 4 cores. The other reported cores are Hyperthreads (2 in core).
As there are only 4 temperature sensors, only 4 are reported in the graph. [0,1] [2,3] [4,5] [6,7).