See below. My back of the envelope math is that there could be about $600B of PPP demand if every eligible business applied for the maximum amount, so the $349B would be just under 60% of that amount.
I suspect that this tweet is intended to slow down the tsunami of applications that is coming on Monday. I will go on record as predicting that this won’t prevent Monday from being utter chaos for banks and applicants. Bold, I know.