Look for sickly sweet in the heads as a newbie it tasted quite good but now :puke-huge: collect in 200ml lots and look for the first jar that tastes neutral. This will be start of hearts, You can either keep this jar or skip one more along the line.
There is no "set amount". For a hearts cut each ferment will be different.
For tails it will creep in taste each jar when you get to one that really makes you screw your nose up,wet carboard smells like a wet dog, that is start of tails.
Personally I dont include it or the last 3-4 before it :handgestures-thumbupleft:
remember you cant cut by someone elses points or your previous runs. Smell and taste and learn to pick heads hearts tails :handgestures-thumbupleft: