Part of your answer is the offset column, which seems to be relative to the
abbreviation used. This implies, to me, that each particular abbreviation
has it's own way of specifying the "starting point" of the time. Added is
the DST flag, which (probably) tells you that your app needs to keep
daylight savings time in mind.
I can't tell you why there are so many, or which one to pick, but there you
go. Just, you know, pick one, learn it's rules and stick to it.
Bier met grenadyn
Is als mosterd by den wyn
Sy die't drinkt, is eene kwezel
Hy die't drinkt, is ras een ezel