...I wonder how you can have so much transactions per second? (the slide shows 500-1500) I read that bitcoin is limited to 7 transactions per second...
My thinking goes this far. Instant Transactions will have the input funds locked by a set of 10 masternodes chosen deterministically. There are 3,500 masternodes.
Therefore 350 (3500/10) Instant Transactions (minus overhead) can be locked simultaneously. If this process can happen a couple of times every second, then 500-1500 is the answer.
If there are any devs watching that want to correct me, please do.
This is true but they have to be in a block later. This part is interesting.
would indeed be interesting to get an answer from a dev

I thought about this a bit more and I came to the conclusion that the part in
bold isn't correct:
the reason is that it's impossible to have through a random process pick 350 times 10 different masternodes at the same time. There will be overlap, so the amount of instant ransactions that can be locked is a much lower amount. I didn't calculate the statistics, but it can be easily calculated:
chances to pick for example 100 different nodes out of a pool of 3500 is:
(3500*3499*3498*...*3402*3401)/(3500^100)
still would appreciate a dev explaining this...