Confused on which Global Variable i should use

In my mod i am creating a block with a GUI. this blocks purpose i to take an input and convert it into a different output. im using a procedure that trigger on Block Tick that will...

1. check for a Logic Variable as False/check for correct item in input slot/check for no items in output slot

if the above is true then

2. set that variable to True

3. wait 20 seconds

4. remove 1 item from the blocks input slot and place 1 item in the output slot

5. set the Variable as False

I have no problems with the Procedures.

My question is what Global Variable Scope should i use for the block.