Ignoring the Oct 25th to Oct 31st difference, if that scenario played out and at the end of January HF sends out one extra module because hey, a BabyJet would have earned 25BTC between Oct 31st and Jan 29th they will have a lot of pissed off customers.
The calculation for how much you have earned is based on the shipping date. By the letter of the program it is the first 90 days, that would mean if it ships 30 days late your MPP window is also extended 30 days which obviously makes the program a worse deal. Many people complained it would be fairer if the MPP began when the units should have shipped so customers are not double penalized for late delivery. HashFast seems to have agreed.
Still the earnings are based on when what a shipped unit would earn each day up to 28 JAN.
They way I read it (and I may be wrong) if your unit ended up costing 50 BTC, they ship it on say 15 DEC and between 15 DEC and 28 JAN you earn*:
> 50 BTC = no additional boards
> 25 BTC & <50 BTC = 1 additional board
> 16.7.5 BTC & <=25 BTC = 2 additional boards
> 12.5 BTC & <16.7 BTC = 3 additional boards
<= 12.5 BTC = 4 additional boards
Maybe Hashfast can confirm or correct me.
* "you earn" is based on the value of daily value of 400 GH/s (like using a mining calculator but looking backwards) not your actual mining which may be more or less (luck, downtime, pool problems, unit gets stolen, etc).400GH earns - ~0.39 BTC per day at current difficulty. In the 47 Days from 15 DEC to 28 JAN at TODAY'S difficulty you would make ~18.5 BTC
It should be safe to assume that by Mid December the difficulty should be up quite a bit more, I think 4 boards should be expected.