Wow... I can't even... First of all, what is your current firmware version?
That bolded part means that if, for example, your system version is 3.7.0-0, the -0 means you do not have a working browser, so you would have to use the No Browser method. If your system version was 10.7.0-32, the -32 means you have a working browser so you would use the Browser method. If the number after the (-) in your system version is greater than 0, you use the Browser method.
I'm now going to try to explain what you asked about the 4.X.X or 6.X.X cart update. The 4.X.X or 6.X.X cart update means the game cartridge needs at least a 4.X.X or 6.X.X game cartridge in order to run in your system. After you do the cart update, you then click on the Decrypt9 (MSET) link and follow those instructions.
This is all pretty straightforward stuff if you've done any kind of reading on 3DS hacking.