7 times 70 =490.
490 fewer than 70 is -420.
But words mean what you want them to mean, so 7 times fewer to mean 1/7th is becoming commonplace.
(edited because formatting swallowed asterisk for times)
(edited because formatting swallowed asterisk for times)
If new is 1/7 the size of the old, then 7 * new = old. It takes 7 times of new_count to get the value of old_count. 1/7th of the old_count. 7x fewer seems like a shorthand, but I'm not a native English speaker.
x times != x times fewer
7 times fewer => multiply by fraction