Default value for `NSGlobalDomain InitialKeyRepeat `?
The defaults for a freshly installed macOS Sierra 10.12.5 (16F73) are: InitialKeyRepeat = 25 and KeyRepeat = 6.

Please note that if running defaults read NSGlobalDomain KeyRepeat before changing the value (either by the GUI or the CLI), then you get an error like this:


  2017-07-04 14:19:02.131 defaults[29186:269276]  The domain/default pair of (kCFPreferencesAnyApplication, ApplePressAndHoldEnabled) does not exist


The step values that correspond to the sliders on the GUI are as follow (lower equals faster):

KeyRepeat: 120, 90, 60, 30, 12, 6, 2

InitialKeyRepeat: 120, 94, 68, 35, 25, 15