Hi Jay,
That form doesn't have a fixed timeframe for how long it'll take to grant the quota, but it's normal for it to take 1-2 weeks on average. I've seen reports on this forum about it taking up to 4 weeks of time in some instances.
To get the mail quota increased will unfortunately only need time and patience from your end.
If there's an urgent need to get it increased, I would suggest looking into the third party
SendGrid.
Cheers!