A stop price on a trailing buy order is to provide investors an opportunity to enter the market much earlier than the trailing marked price.
Eg: If the current price is $100 and your trail amount is $2 above the current price. This makes your buy stop amount at $102. What happens is if the market turns against you immediately after you enter your order, you will need to wait for the price to reach $102 before the system automatically generates the buy order for you.
What you can do here is to put a buy stop amount at $101 so that your order gets triggered before your trailing buy amount gets hit.
The following is an easy illustration for comprehension:
