For Boil Buoy, there is 15% influence up for grabs in presales, and 1492 units to hit threshold. So at minimum, everyone would get 0.01% influence per unit (15% divided by 1492). These numbers change for every product, but the formula is always influence percentage divided by threshold number.
In order to get influence for a presales commitment, you have to come back to Quirky and complete your order. We send an email when it's time to do that, and we set a window of time to do it. Once that window of time closes, we lock down presales influence. Only the people who complete their orders in time would be awarded influence. (We send 2 follow up emails to warn people that time's running out, so we try our best to make sure nobody misses out.)
At that point, influence is calculated by dividing the influence available for presales (15% for Boil Buoy) by the number of units that actually gets ordered and paid for.
I'm gonna get hypothetical now. IF people end up completing orders for 1000 units of Boil Buoy, then each unit would net an influence of 0.015% (15% divided by 1000). If you order 5 units, that would be 0.015% x 5 = 0.075%. And so on.
Does that help?