I know this is a silly question, but to be honest I have not looked into the logic much deeply. That being said, here's my question.

With ecm, if you run the calculated number of curves for a digit level, does it guarantee that there is definitely no factor for that number with digits less than or equal to that digit level?

From Mystwalkers post, for example (and assuming the calculations are correct - not that I doubt them btw), does running

3155 curves at 50 digit level guarantee that there are definitely no factors with less than 50 digits? Or the same with 55 digit level: 17899 curves case.

Or, is there still a chance (althoughy slight) that there might be a factor with less number of digits?

And, another way of looking into it, let's assume its theoretically and practically possible to continue the search until 155 digit level. Then could one say, with the calculated number of curves, ecm would definitely find "the factor".

And one last other way of looking, if it were to find no factors until 155 digits, would it be possible to assume that 24737*2^991+1 is infact, prime?


PS: I'm not suggesting anything. Just trying to understand the logic.