I just wrestled with this problem trying to file my return...then I found this discussion...which took me a while to find, but that's a separate issue. Anyway, I replaced the $300 with $600 during the review process and then DID NOT review again. The $600 value stuck and I was able to file our return without further problems. I agree that this is definitely a bug and, as a retired programmer, I would think it would be a fairly easy thing to fix (eg, IF married filing jointly, $600, ELSE, $300)!
