Self checkout lines...

kris
Today at the grocery store, I went to checkout at the self checkout. There are 4 registers for this 1 area. All 4 are occupied so I started a line to wait for the next one. A couple minutes later this older guy comes up and goes to stand behind one of the registers where a lady is almost done checking out. When there's a self checkout area do you line up individually behind a register or form 1 line for all 4 registers? What would you do?