I think the multiple values are the results obtained by different people using different methods. At the very right of the table under doi you can find links to the papers where the values were presented.
Thanks for the reply! I was thinking the same thing, but how should I interpret this? Shouldn’t this be a precisely defined quantity? There is some range on the reported values, so it seems hard to mention a single value as “the” correct value.
I agree that the different studies give different values for the quadrupole moment. Anyway, IAEA seems to make a difference between the compiled values of the moments and the recommended ones. It seems that all the data are up to evaluation and that the publication cut-off only selects one of them. If you go to the levels tab, and you enable “comments”, then you can see that different data are available.