Appraisal came back at my low ball offer

[Alexis A Peinado]

I made an offer of 130k on a duplex that was listed for 200k, it was approved by the seller and we began escrow. However, the appraisal came back at 136k, I'm wondering what I'm missing here? My intension is to use the BRRRR method but now I'm not too sure what this means for me? Has this ever happened to someone and what was the outcome? I don't know if to worry!