The TMS means time multiplier setting.
It determines after how much time the relay should operate.
Lower the TMS, faster the relay operation time.
Now in the book pg 5-8, the author has not mentioned the formula of plug multiplier setting
Plug Multiplier setting=Fault Current/Plug setting(pick up current)
In page 820, what the author wants to say is that for TMS of 1, the relay would take 2 seconds to operate.
Then in order to make the relay operate at 1 second, the tms should be what?
So earlier for tms of 1, the relay would take 2 second to operate. Now for tms of 0.5, the relay will take only 1 second.
Lower the TMS, faster the relay operation time