I've got a big problem with my timing, I would be thankful for some help

I use a metronome
I got it on 4 beats per measure, so I strum 4 times
1, 2, 3, 4.

But I get confused at these tabs :



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Does the open D counts as a 1 ? Or is it the A (second fret, G string) that counts as the first beat ?

I'm really confused and don't know whether I am doing right or wrong
How do I know what and when to hit a note ?

I would be very grateful for some help
I'm in a college band aswell, I try my best to listen to the drums but just can't get to it which is really frustrating for me and the members of the band

Thank you