In the test file at [1], the XY (scatter) chart has point labels A, B, C, etc. If you remove these labels (right-click on the line -> Delete Data Labels) and add them again (right-click -> Insert Data Labels), numbers are shown instead. These numbers do not correspond to the selected Data labels series, but to the X values. 1: https://ask.libreoffice.org/upfiles/1395709989531115.ods
I've reproduced this problem with LO 4.3.1.4, 5.0 and 5.1.0.3. I'm saying this is a regression since on the Forums two users were able to create the linked document in 2014 (no precision about the version): https://ask.libreoffice.org/en/question/31880/data-labels-on-data-series/
Created attachment 123415 [details] Test file with modified data values. Hi @Milan, thanks for reporting. After deleting and reinsert the right Y values are inserted. (in your sample X and Y has the same values for every point) Edit the with right-click 'Format Data Labels' 'Data Labels' disable 'Show value as number' and enable 'Show category' It works fine for me.
Closed as 'worksforme' please if you are not agree reopen it.
Thanks, so in the end that's not a bug! I still believe this is not the best behavior, since the categories which were specified manually are not used by default. Also, in a scatter plot X and Y are symmetric, so I don't see why you would like to show values for Y but not for X. But then the most important enhancement to XY charts would be to fix the wizard to detect when you want to pass a categories column, and use it for labels.
I've just filed an enhancement request instead as Bug 98543.