Poker Tracker Auto Rating Has Me As TAG/Passive

[mjm]

I've just started to play some low limit ring games on stars 2 days ago, (blinds 1/2) buy in $200. I have been 3 tabling and been on a bit of a heater with profits of over $2k on the two days (I know it won't last).

I have input the hands into Poker Tracker and after 1300 hands it's auto-rate (set at the auto levels) has me as tag/passive.

I don't really know how the auto-rate works but being rated as passive post-flop, does not seem a good sign (although I am very happy with my limited sample results).

I also lost a decent sized pot to a player who I hac already noted as a good player, when I folded to his strong river bet, he commented in the chat box that he knew there was no way i'd call from my betting on the earlier streets.

Basically my question is 2 fold:

1)Can I make any inferences from a sample of 1300 hands.
2)Should the fact that i am auto-rated as passive post-flop concern me (and require significant revaluation of my game), bearing in mind I am very happy with my results thus far.

Thanks