Agreed, this is an abstraction, but the moves are per SR (3m per SR, starting the DEX SR), all the actions are per SR, spell casting has a duration in SR, ... We almost have the impulse system of Ringworld, with the exception of the End of Round with no carryover, except for the actions that have a duration of more than 1 round (Spell casting for example). This is why I explained it is easier to explain to beginners (in my experience), because if 1 round is roughly 12 seconds, 1 SR is an abstraction that covers roughly a bit more than 1 second.