what is suggested by the language used is what is meant.
the payload - a small probe - is supposed to travel far enough to get into orbit around the Moon, which is on average 238,855 miles (384,400 km) from Earth.
the launching rocket is supposed to keep pushing/accelerating this probe until they get to 80.000 miles from Earth, where having reached a speed of over 23,000 miles an hour, they part company and the probe keeps moving by inertia to get near the Moon and in orbit around it.
The inertial movement of the probe starts AFTER reaching 80.000 miles distance from Earth.
BTW, there is no "IF" - I found and watched the movie. It starts by news about a fictitious probe "Pioneer" supposedly sent in November 1957 to orbit the Moon. IN reality there was a "Pioneer 0" probe sent by the United States Department of Defence on 17 August 1958
https://en.wikipedia.org/wiki/List_of_lunar_probes#1958–1960