You can think of this strategy as simultaneously buying one long call spread with strikes A and C and selling two short call spreads with strikes C and D. Because the long call spread skips over strike B, the distance between its strikes will be twice as wide as the strikes in the short call spread. In other words, if the width from strike A to strike C is 5.00, the width from strike C to strike D will be 2.50.
Whereas a traditional long call butterfly is often used as a neutral strategy, this strategy is usually run with a slightly bullish directional bias. To reach the sweet spot, the stock price needs to increase a bit.
Selling two short call spreads with half the width of the long call spread usually makes this strategy less expensive to run than a traditional butterfly with calls. The tradeoff is that you’re taking on more risk than you would with a traditional butterfly. If the stock continues to rise above strike C, your profit will decline at an accelerated rate and the trade could become a loser fairly quickly. That’s because you’re short two call spreads, and there’s half as much distance between strike C and strike D (short spreads) as there is between strike A and strike C (long spread).
Ideally, you want the options at strike C and D to expire worthless, while retaining maximum value for the long call at strike A.