need good database structure for tracking counter state

Dear,
Can anyone help me to make good database structure?

What i have are some locations where I have some machines. Every machines
have 2 counters (IN and OUT). I need to be able to enter state of that
counters and after that to compare that values with previous entry IN and OUT
counters.

How I see it seams that somewere I need to keep information wich machine is
on wich location. Beside that I need to track information about date and time
of entries.

Situation:

Location 1 - machine1, machine2, machine3
Location 2 - machine4
Location 3 - machine5, machine6, machine7, machine8
.....

I need 3 kind of reports:
â—‹ Deference between new IN / OUT and some old IN/OUT counters for every
machine
â—‹ Total IN/OUT for some location
â—‹ Total IN/OUT for all location

How I need to organize this datas?

Thanks for helping me,
akioki