That's a very favorable reception environment.
Have you read many of the older posts here? One consistent theme is that an attic is a poor location for your antenna and will have unpredictable results.
Have you tried your reception with an indoor antenna?
There are lots of confounding circumstances, but you should be able to pick up all the green highighted channels with a good indoor antenna. I'm not an antenna expert (just an interested participant trying to contribute) but I would expect your attic installation would not be a whole lot better than indoors reception.
Realize that there are two bands for TV broadcast, VHF (2-13) and UHF (14-69) and there are different coverages with different antennas. You can look at the Antennacraft site and get a feel for this.
http://www.antennacraft.net/ Look at the channel listing in your TVFool radar plot and see if there are any channels you must have that are VHF or are widely separated from the main group of UHF channels. If you really want WGTV, for example, then you'll need an antenna with high VHF capability.