This is the value of the position in money game, e.g., if your equity is +0.4 an you are playing money game with a $1 stake, you will win $0.40 on average. The money equity can be calculated with or without taking the effect of the double cube into consideration, or cubeful or cubeless. The cubeless equity can be calculated from the basic formula: 2*p(w)-1+2(p(wg)-p(lg))+3(p(wbg)-p(lbg)). Evaluating the cubeful equity is much more difficult; it can either be estimated from the cubeless equity by using transformations as outlined by Rick Janowski or by constructing a neural net that directly outputs cubeful equities. GNU Backgammon uses the former approach (Cubeful equities).