OS before Market Close: 4.5 bil, Market Cap: 4.5 x 0.0017 OS after Market Close: 3.1 bil, Market Cap: 3.1 x 0.0017 (~0.0025 to keep market cap the same as before market close)
In order to keep the market cap the same after OS reduction, stock price needs to be between 0.0024 and 0.0025.