About 80% of the way down in the Star Trek II: The Wrath of Khan movie script,
[Reliant bridge]
JOACHIM: If they go in there we'll lose them.
KHAN: Explain it to them.
[Enterprise bridge]
SAAVIK: That was close.
KIRK: They just don't want us going in there.
SPOCK: One minute to nebula perimeter.
After Khan's "Explain it to them" command, the pursuing Reliant fires a shot towards the rear of the fleeing Enterprise. This occurs at about the 0:53 point in
Khan's statement, and that there's only one shot fired, implies it has a symbolic meaning. I believe this was meant to be something like "A shot across the bow". The Wiktionary shot across the bow page gives a reasonable idiomatic meaning of
A warning that negative consequences will be faced if something is carried out or allowed to continue.
This fits with Khan's statement of "Explain it to them" (although this is redundant since Khan would know that Kirk already realizes there are negative consequences, regardless of what Kirk does or doesn't do). Nonetheless, the potential "negative consequences" of the Enterprise entering the Mutara Nebula would usually likely be less than if the ship remains outside. Also, although Kirk's statement of "They just don't want us going in there" would fit my proposed meaning, even a close shot from behind will not cause the Enterprise to change its course much, if at all, or do anything else to slow down its approach. If anything, the Reliant firing on the Enterprise should cause Kirk to want to enter the nebula even more for its relative safety, thus doing the opposite of what the potential stated intention is!
My question is if something similar to "A shot across a bow" is basically the intended meaning behind Khan's statement & the fired shot and, if not, then what does that scene mean, e.g., it was just included for dramatic effect?