Bienvenue sur GTA5-Mods.com

Lovely addition, I'm just stuck trying to import sounds.
Bit confused, do I copy the exported openformats files and their accompanying folders back into the .rpf's from where I exported them, or...?

Question: I've noticed in train speeds and stopping at stations, in the normal speed folder, there's a traintracks.xml that contains a reference to a 'trains13.dat'
There are only 12 in the game without mods, and Improved Trains doesn't come with another one, so what's the extra line for?
trains13 reference details:
<train_track
filename="common:/data/levels/gta5/trains13.dat"
trainConfigName="freight_group_2"
isPingPongTrack="true"
stopsAtStations="false"
MPstopsAtStations="false"
speed="8"
brakingDist="10"/>

So, something's wrong with one specific part of the scenarios from what my winmerge comparison between content.xml files gathered.
Why is that?