Is there any case where your interpretation makes sense? Would you ever say 0.86 times fewer instead of 0.86 of the size?
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.
When value is above 1, it's not really ambiguous anymore as only one interpretation makes sense. But I understand that it could still be incorrect, if it's not well defined term in English.
(edited because formatting swallowed asterisk for times)