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The instructions you're following (pasted/linked) are for the official EVE Launcher.

If you want to use ISBoxer EVE Launcher ("the EVE online launcher made for ISBoxer"), then don't follow the instructions you linked at all. Don't use Add Game at all.

Instead, you would want to go here... https://github.com/LavishSoftware/ISBoxerEVELauncher... and after downloading it, you would scroll down to the part where it says "Recommendations for ISBoxer". ISBoxer EVE Launcher handles all of the "Add Game" for you in Step #7.