They multiply the base value for cost of specialties and gain rate by the amount you enter. 1.5x cost means you need more XP to get a specialty, 1.5x gain means you gain more XP. Honestly I think those are pretty self explaining.
The cost of the specialties and the gain rate of skill points, which seems pretty obvious to me, especially given the descriptions in client and server ui. I'm glad you found a description fitting better than the one in the Server UI for you on Discord though. Just keep in mind that the wiki is a community wiki, so everyone can add information they think is understood better :)
But that is the case, if you hover over the settings in the client it will give a description for them and the Server UI also has a description for them. The config files itself cannot contain descriptions, to make it easier the config variables are mostly named in a self-explaining way. Everything you are asking for is already there.
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