Arm Over vs Unsupported Lengths

[DavidK7107]

For the purposes of this question I'll reference NFPA 13 2019 edition, and the pressure is below 100 psi
17.4.3.4 Unsupported length between the end sprinkler and the last hanger on the line shall not be greater than 36 inches for 1 in pipe.
17.4.3.5.1 The cumulative horizontal length of an unsupported armover to a sprinkler, sprinkler drop, or sprig shall not exceed 24 in for steel pipe.

Does this mean that if you have a 48" armover, the armover must be supported per 17.4.3.5.1, and the hanger must be within 36 in of the drop to the sprinkler.
Or is there something here that is supposed to mean that the hanger on an arm over has to be within 24" of the sprinkler.

I realize that per 17.4.3.5.2.3 where pressures exceed 100 psi that the hanger shall be installed so that the distance from the end sprinkler or drop is not greater than 12 inches. But this type of comment does not appear under section 17.4.3.5.1. Can someone please confirm that a 48" arm over requires a hanger within 36" of the sprinkler drop per the requirements of 17.4.3.4 and 17.4.3.5.1
I mean, it doesn't really matter anymore, I installed the hanger within 24" of the sprinkler already so that we can clear our inspection. But for educational purposes and future reference Let me know what you think.

 

[UFT12]

You need to differentiate the “unsupported length” from “unsupported armover length”. These are not the same.

Unsupported length as referred in 17.4.3.4 is meant for the last sprinkler on a branch line regardless of having a drop or sprig.

Unsupported armover length as referred in 17.4.3.5.1 is meant for any intermediate sprinkler on a branch line or main that typically is required for a drop (e.g. obstruction) or a sprig (e.g. ceiling pocket). Observe the term “cumulative” for the length. A pipe with elbows becomes more flexible and therefore a lesser max. distance for the hanger is mandated.

There are some indicative pictures in the explanatory material too.