I'm about to evaluate my survey and filter certain answers. In doing so, I came across the marker for LASTPAGE.

My survey has 5 pages plus the start page.

Out of 2197 entries in the survey, I got a value of -1 for last page 39 times. What does that mean? I also have regular replies for some of these entries, but SUBMITDATE is always blank.

Also, I have 0 for Last Page 714 times. Are these the ones that didn't get past the home page? However, I have at least some answers for 2 of these people. SUBMITDATE is always empty.

PS: This question is not about design, but there's no dedicated board for answers/analysis.

Just give it a try!
Open the survey and
a. close the browser immediately on the welcome page,
b proceed to the first page and close there,
c. proceed to the first page, go back to the welcome page, close.

Compare the values of "lastpage".

Joffm 

And do NOT double post!

Unfortunately, my survey is already closed and I do not want to re-open again. Also, we deactivated multiple responses.

But from the suggested actions I see that I missed a possibility (namely c).

So I guess a) leads to 0, b) leads to 1, and c) leads to -1.

Thanks.

Unfortunately, my survey is already closed and I do not want to re-open again

Of course not.
Such things you do in a small test survey.

Joffm