The standard Iveco Turbostar Fuller Shifter was by default the 13 speed 14613 or 15613 on late versions.
The gearbox had 4 low range gears with no splitter and then on the high range, other 4 gears with splitter. The shifter had in fact 2 Crawling gears.
The hi range crawl was a gear placed between the low range 4th gear and the hi range 5th.
Eaton itself advised against the use of the hi range crawl. However many drivers were using it very often, because it was faster to engage than the hi range 5th.
This feature is available in the mod, including a “Fuller 13” Gearbox Layout that can be placed in the profile folder.