The first Vivint matching period is from the beginning of 21st (00:00 MST, 05:00 GMT/UT) to the end of the 22nd - eg all of today, Thursday, until the last minutes of tomorrow, Friday. During this time, Vivint will match all donations made via the charity voting page in their special matching periods.
They will match all individual donations up to $50/£30, to a maximum of $2,500 per charity. They are passing all monies on, doubled, without deductions. You will be able to see how the WPI donations are going, and make a donation yourself if you want to, on the page where you cast your vote.