How the code works
The example posted here gives just a short example of what it should look like and only details what it could look like for a few levels. In order to raise the level cap you need to extend it (write it out) all the way to whatever max level you would like with increasing xp requirements.
[/script/shootergame.shootergamemode]
LevelExperienceRampOverrides=(ExperiencePointsForLevel[0]=13,ExperiencePointsForLevel[1]=20,ExperiencePointsForLevel[2]=30)
What this example is showing is for the part there it says "ExperiencePointsForLevel[2]=30" this broken down means that Level 2 requires a TOTAL XP of 30 to reach (NOT 30 xp from level 1 to 2). With level 1 requiring 20 XP this would show that to get from level 1 to level 2 there is 10 XP points inbetween. So if you were to extend this to level 3 and you wanted it to be 20 XP points from level 2 to level 3 it would look like this "ExperiencePointsForLevel[2]=30,ExperiencePointsForLevel[3]=50" which makes it easier to set the XP requirements for each level although keeping track of the amount of XP between levels becomes a little difficult.