Can you figure out what the answer is?

Examine the response provided below:
In this instance, the missing number might be compared to the gears in a typical manual gearbox. Taking into account that manual transmissions often have a setup like this:

R is an acronym for reverse.
1. (Basic equipment)
Second gear is the third gear.
Fifth gear is 5, Fourth gear is 4.

The reverse gear position—which is often denoted by the letter “R”—is absent, and the positions correspond to gears when the absent number does so.

Consequently, R stands for Reverse and is the “gear” that is absent when considering the order and the idea of a manual transmission.