DME to fix F-up...???

hi folks. long story short...
I felt my boil off was too much on this all grain batch so I topped off in the kettle during boil.. now after I removed my chiller I have 5.5 gallons, but my OG is 1.050... per beersmith, I am now only at 52% efficiency and my estimated ABV will be 4.2%.. this is an oatmeal stout.

measurements:
pre boil gravity = 1.044
into fermenter gravity = 1.050
into fermenter estimate PER BEERSMITH = 1.064

I want to get to 1.064...
1. should I add DME to fermenter?
2. If so, how much?

thanks!!

You could boil up some DME in water, cool it, and add it, but I wouldn't add straight DME/LME to your fermenter.

Overall, I would chalk it up as a learning experience and leave your fermenter alone. I have no problem drinking 4+% stouts - just means I'll drink two in a row

LOL. true. can never have too much Stout