question about the documentation

[Till Rettig]

Hi,

while translating I found this sentence in the Docs Version 2.11.23 chapter 6.1.7:

"In the example below, the first check passes without incident, since the e (in relative mode) is within a fifth of a'. However, the second check produces a warning, since the e is not within a fifth of b'. The warning message is printed, and the octave is adjusted so that the following notes are in the correct octave once again."

What does the fifth do here? Wouldn't it be better to say: "inside the same octave" or something like this?  It seems I don't understand this passage. Why is it suddenly a fifth and not a fourth anymore?

Greetings
Till