Either type can have many flowers set at once. Come look at my garden, well after the heat wave that is.
Not too many flowers setting now, they don't produce much after around 90 or so degrees.
But I do agree on the determinate as well based mainly on the fact that they were from a hamburger. Now I am assuming this a restaurant hamburger. So give me some space here.
If it is fast food I would almost guarantee it is determinate but you never know. Those places get the majority of tomatoes from places that more than likely grow determinate. Most if not all of there fruit ripen at once which makes picking and therefore shipping and therefore making money faster easier. If you have to wait around for fruit to ripen that time is money.
It will be interesting to see what comes of this, please
keep us informed.
Lots of "if's" here, so it is hard to say this early in the game.