There was only one lineup at the McDonald restaurant for all the counters/tilts.

[michael281001]

1) There was only one lineup at the McDonald restaurant for all the counters/tilts. This is how the system work, as soon as the next counter/tilt become available the employee will call the most front customer in the line to go forward.

2) There was only one lineup at the McDonald restaurant for all the counters/tilts. This is how the system work, as soon as the employee is done serving a customer, the employee will call the most front customer in the line to go forward.

[5jj]

Please make it clear what you want us to do. I am guessing that you want to know which of these sentences is better, but we shouldn't have to guess

1) There was only one lineup/queue (BrE) at the McDonald's restaurant for all the counters/tiltls. This is how the system works,: as soon as the next counter/tilt becomes available, the employee will call the most front first customer* in the line to go forward.

2) There was only one lineupqueue (BrE) at the McDonald's restaurant for all the counters/tilts. This is how the system works,: as soon as the employee (is done)/has finished serving a customer, the employee will call the most frontfirst customer* in the line to go forward.

*or: customer at the front/head of the line/queue.

Both are now acceptable.

[SoothingDave]

or "the next in line"