Please someone explain /click and macro keycombo

[JackBurton]

Im trying to grasp how to save key real estate using the "allow extra modifiers" and !if (character in "Action Target Group Name Herel"), actualy i allready fully grasp the !if (character in "Action Target Group Name Herel")
part its just the boxes thats making my head go in circles. and /click stuff.
Key Combination: 1

Allow Extra Modifiers - for example for this In Game Helper > World of Warcraft > Macro to work properly i must have ALT, CTRL, and SHIFT checked. preferaly the left side ones since thats the hand i use.

#showtooltip
/cast [nomodifier] <Mount of your choice>
/cast [modifier:ctrl] Find Minerals
/cast [modifier:shift] Find Herbs
/cast [modifier:alt] Smelting

Can use FTL Modifiers - when you check this does it blacklist me from using ctrl-1 ctrl/shift 1 or whatever as an another isboxer game helper macro?

For Example Focus {FTL} game helper macro has all check boxes "allow extra modifiers" and "can use modifiers" checked off. If can use FTL~ is checked off why need to check off allow extra modifiers?