IV push med

Need help!!!please

we just learned about push meds and I am confused about couple things

1.when pushing med through the extension set and the rate is 2.5 ml over 1 min

a) let's say,I am flushing the extension first and the extension set holds 1 ml

So,when I start my med push,should I start timing it after I have pushed 1 ml of the medication?

because I was told tht we have to time the flush after the med is given because there is still medication in the line .If that's the case then, after the first flush there would still be 1 ml of saline in the line .So I would need to Start timing after I have pushed 1 ml of med to clear the saline right?

2)If I am also timing the post flush for 1 min and there is still medication on the line,do I have push that for the same amount of time?if I do that then the total amount of time would be more than what the IV book says !!

Please clarify .I might be overthinking but I can't understand this concept