The Loadout is 168 rounds. Enough to fill 6 magazines with 28 rounds each.
Why 28 rounds and not 30? When your bolt is forward as you attempt to reload, there is not enough room for the magazine to firmly seat correctly and consistently.
Removing 2 rounds relieves this spring tension ensuring your magazine engages the magazine catch/release eliminating this problem.
This also requires less force to seat the magazine. When changing the magazine it will be easier to get another magazine properly inserted and get the gun back up and running.