Astronomy / Space Question about spectral type classification

I'm currently trying to understand the spectral type nomenclature as seen in our galaxy map. Here is an example: a K (orange yellow) star with the complete notation "K3 VA, KO VAB". For a start I could find an introduction here:

K3 is clear so far, but I still can't understand the remaining 'VA, KO VAB', even after reading the page from the link above. Can anyone shed some light on it or a link perhaps to some further informations? With the exception of the link above, all I could find about the topic were astronomy books.

Thanks in advance! [smile]
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