It's just how much above average the zonal component (u axis or east-west) wind is. Easterly is a negative wind (-u) so basically that area has an easterly component >14kt above normal. I don't really care for those maps. I'd rather see standard deviations.
OT but I like following your station when I check in on mine. You do run relatively cool up there. That benefits you in winter, but not during warm season. You’ll probably be 85 when BDL is 90.