250 response limit (free acount) is not clear to me

Hello everyone, I have had this free account for years now. The limitations seem to change whenever I come back to Qualtrics, and right now I'm having issues with the 250 response limit - which I hadn't noticed before (I could swear the only such limit was 100 responses per survey). The issue I'm having is that I don't understand this limitation. Do I get: a) 250 per survey; b) 250 responses across all surveys; c) any of the above, and the used-up responses decrease as I erase them from my survey(s); d) a or b, but they don't decrease ever (e.g., one-shot). The only other thread I found on this topic wasn't very specific: https://www.qualtrics.com/community/discussion/6041/does-deleting-responses-decrease-the-allowed-responses-counter Does anyone know for sure? I have a survey to run and whether I use Qualtrics or something else depends on how the ambiguity (or just lack of details) is resolved. Thank you very much. J.