If you decide to quit protection early, then you will receive a metal and oil production boost. The amount of workers used to produce metal and oil per tick is increased by 50%. The length of this bonus depends on how many protection ticks you have left multiplied by 3, e.g. breaking protection with 100 ticks of protection left gives you 300 ticks of this bonus.
unrelated answer, and incorrect. Production boost length = protection tick / tick speed * 3. So if u have 100 tick of protection left on 1 ticker, u'll have 300, but if it's a 2 ticker then u only have 150.
now to a more related answer, if u have 300 production boost from breaking protection, and u buy a production boost with blue tokens, u'll have 300 + 200 = 500 production boost.