I will try to explain this in simple terms. You did not get shares, you received a value. That value was converted to shares based on current price minus taxes. Your value due over the 120 days will not change.
So here is a simple example not using taxes. Your piece of the equity (value) stake was 2000 dollars. Let's say the stock price opened at 1 dollar. So yesterday you got 1000 shares. If over the course of the next 120 days, the price of the stock stays at 1 dollar, you would get 1000 more shares for a final value of 2000 dollars. Now let's say the price of the stock in 120 days was $1.50. Your current value would be 1500. You would then receive 334 shares to make up the 500 dollar difference between your current value and the original value of 2000 dollars. So if you do not sell any, at the end of 120 days, you value will be 2000 regardless the current price of the stock.
Does that make sense?