okok got it.
The github contains some of the formulas but it is pretty scattered.
For the current power used,
where w_p is the weighted power, the 0.49%/50 in some sense corresponds to the price you need to pay to cast a vote (in terms of your VP). I am curious if this formula will still remain or if the 50,000,000 is meant to replace it.
They're also changing a lot more about how the voting system works in switching to voting mana, so I have no idea. I'm guessing that .49/50 is there to handle some weirdness that comes at very small vote sizes, and/or stop people from exploiting vote quantization, which is something else I don't understand very well. I don't think it's related to dust votes.
The 0.0049/50 is VP that is not represented in the value of the vote since the value of the vote is given by w_p times a constant. So if you are voting a lot ot low weigthed votes instead of high weigthed votes then your VP is going to be lower.
In addition, if you would want to optimise the votes that you can get out of an account in a single date then this 0.0049/50 ensures that there is a max amount votes you can cast. If you cast more votes then that then the total value of votes cast will be lower. This has something to do with the weirdness that comes at very small vote sizes. :)