Mann-Whitney

[JuleinMalang]

Hello! My question is rather into Interpretation of Mann-Whitney in PSPP, maybe
somebody can help. Would be great! (:

I performed u-test.
My Syntax:

NPAR TESTS
/MANN-WHITNEY = age BY sex (1, 2)

As a result it showed "Asymp. Sig. (2-tailed)" = 0,00 , z was infinite.

To me that means, that the groups are significantly different. Which was
confusing me, as they are almost the same. So I calculated again in two
different Browser-Programs. Both showed p(2-tailed) = 0,91 and z = 0,11 Which is
much more probable for that data.
Does anybody have an idea what I could have done wrong?

Thank you!