There is absolutly no stupid question, only question that needs answers.
Depends on when you already submitted your site.
Most of the time, the SE allow several submission.
What they are absolutly not tolerate is spamming their system.
Few years ago, some people believed that with hunderds submission per day, their site would be everywhere in SE. They were wrong. They were banned.
Nowaday, there is a small flexibility. A site can be submited several time per year. Accordingly to some newspaper the fact is simple. Some domain name already expired 10 times since the first website and were bought by 10 differents owners. None of them can't be sure that their domain name wasn't already submitted to SE-.

Anyway, the safest way for you is certainly not to use this service. But, if you decide to try it, don't be worry by this statement from SE. They won't ban you if you waited, let's say, 2 weeks between 2 submissions.

Just my 2 cents.

Anyway, your second question after this one should be: To how much FFA my site will be submited. Because here th risk may be higher to be banned from particular SE and, not the worst, you'll get spammed by these FFA.