How did the lunar module get back to the command module if the only had about 15 seconds of fuel when they landed?

The lunar module (LM) used a small amount of fuel to lift off from the Moon's surface and return to the command module (CM) in lunar orbit. After completing the lunar surface mission, the LM's ascent stage ignited its engine, which was designed for a brief burn to achieve the necessary velocity to rendezvous with the CM. The LM's ascent stage had carefully calculated fuel reserves, and the astronauts executed precise maneuvers to ensure they could complete the ascent and docking with the CM. Ultimately, the LM successfully returned to the CM despite having a limited amount of fuel.