Harvesting 3 days early?

What sort of weight are we talking i would loose if i had to harvest 3 days early? Oz,s or grams?

Typically grams. More than reduced weight, the problem with early harvest is immature buds. A couple grams lost doesn't matter, but most of the bud on the plant producing a less enjoyable smoke does matter. That said, a few days shouldn't affect the finished smoke that much. Depending on what's preventing you from finishing on time, you might be able to leave them in longer with the lights off, or some other way around the problem.

how in the world do you know your 3 days away? lets see a pic ill bet your 3 weeks away. im assuming your counting the days and going by breeder suggestion, right?

No I'm Goin by the microscope checking all the trichomes there all milky but not Amber pal. 8 weeks flower uk cheese some how can't see me being 3 week out!

You shouldnt loose anything because they barely add weight in the last week-10 days anyways. Just make sure you've flushed early enough and you're not taking 3 days off the flushing time or else it might be more chemically and crackle when it burns