I've never participated in something like that, but it looks to me like the raised amount is tracked and displayed automatically, no need to put in your own numbers. Or if you mean start off with a non-zero number, you could go ahead and just make an initial purchase, otherwise would seem kind of dodgy.
Viewing post in Sales - Partial earnings goal
Yes, I did mean start off with a non-zero number. I'm I'm trying to raise money for something but I already raised part of the amount I need in previous sales or even from other platforms, starting with a non-zero amount would allow me to display not just the value of the goal but also how much progress had already been done toward that goal overall. Say instead of starting with $0/$1.000 you could start with $100/$1.000 for more transparency.