Let's Control It

I'm wondering when using a timer in the rules' section, will another use of the same timer 'extend' its time?

E.g.
timerSet,1, 1800 // something ON for 30min
waiting for let's say 10min
timerSet,1, 1800 // something ON for 30min

On Rules#Timer=1 do
// switch OFF the 'something'

Would the 'something' then stay on for 40min?

When setting a timer, the newly set value will be the time it takes for the event to be generated. No extending or adding. That would only be confusing.