Thank you, we are glad that you are interested! Good question!
You are right — first come, first serve.
There is no restrictions or upper limit on the purchasing amount (Except for the total amount reserved for the entire program. The max amount of token reserved for Options program is 10,000,000 in USD equal,inclusive of bonuses 11,700,000 tokens).
If during the option purchase (certain investor) first 20% of max cap finished, an investor receives remaining options that guarantee their holders a 20% bonus. So, during a single purchase investor may receive options for the first 20% of the maximum option cap, and options for the next 20% of the maximum option cap.