Vvvfl?

I took a "5 days early" test today at 10dpo & the directions say to look after 4 minutes. I glanced after ~1 minute & clearly saw a faint line, but by 4 minutes it had faded to so faint it felt like line eye. Does it count before the time window is over? I always assumed the time window was so you didn't falsely think it was negative, I've never seen a false positive from looking early before...