SMAX default Value in Quicktune Script

Hi all,

I don’t know if this is the right category for this, but I was wondering where the 50 as a default value for the _SMAX parameters comes from in the Quicktune-Script:

Does anyone know?
Git Blame tells me that @tridge last edited the relevant line https://github.com/ArduPilot/ardupilot/blame/master/libraries/AP_Scripting/applets/VTOL-quicktune.lua#L204