I don't for your situation entirely, but usually we don't allow people to skirt around using racial slurs and an admin will usually give a warning not to push their luck if people are using words that sound/ read close to slurs.
So in terms of “joking” about saying a racial slurs, in the past at least people have used other forms of slang/short version of racial slurs as an alternate form to use in chat to bypass actually saying it which is frown upon. In this case if you’re just randomly saying “Nigeria” and not using it to refer to the Country then they (The admin online or players on the server) can take it as if it’s being used as an alternate form of a racial slur such as in this case. You were also gagged for the reason of “Cap Spam”, which refers to the repeated use of capital letters consecutively in sentences which can easily be combined into our sentence or not just capitalized in general.
Regarding your mute/gag since I was searching through your chat log if you did ever get that answer of how long your mute is, it can be found in sourceban located here. There’s a stacking system to the punishment so you are muted for 3 days and gagged for 1 week respectfully. Should you feel that you were gagged/muted unjustly you can always appeal your gag/mute here on forums under the “You Are Banned” tab using the appeal template located here