Looking at your calculations, why is your sensitivity modifier different for the Str 12 sensors than the Str 10?
You've got an EM Sensitiviy of 5 giving a modifer of 0.5 for Str 10 (which is correct), but 0.42 for Str 12 (whic is incorrect).
If you correct that column, you'll get
Str Size Sens
10 * 10 * 0.5 * 10000 = 500,000 KM
12 * 10 * 0.5 * 10000 = 600,000 KM