it’s not just the unseen movers. Little ole me could not help but notice when trading through Schwab when I bought something through them the transaction would always take 3 or 4 days. The settled price was always the highest quote for that period. When selling the contrary was always true. Stick it Chuck.
I also watched the market depth activity (at Schwab) and set my order limit at a price which I like but which will get executed. If the market moves away, I make a decision to either raise the price by cancelling and re-entering the order or leave the order as is to see if the market comes back to me.
A limit order at a specified price will be executed at my price or better...or it will not be executed at all.
Once executed, the stock is mine, but the transaction settles over the next three days. In fact, if I want, I can resell the stock before the transactions settles.