long tail keyword variations question

I have a long tail keyword, composed of 3 words, let's say word A, word B and word C. This are the stats

A B C: Search Volume: 6600 - Google Exact Results: 16.100
A C B: Search Volume: 6600 - Google Exact Results: 980
B C A: Search Volume: 6600 - Google Exact Results: 0

Those three are the only variation that make sense.

Why while the three variation have the exact same search volume they have very different results in google?

I think that this is some kind of error, and I'm not sure which one do I have to choose. I'm tempted to go with the one that have 980 results.

What do you think?