need one time 300 capacity meeting with Pro account

Hi @ttohmo 

You would need to purchase a large meeting add-on for your account. Unfortunately, there are no 1-day offerings, so you would need to purchase it for 1 month (the minimum) and cancel it before it renews. 

Be sure to assign that add-on to your profile if you go that route. 

Hope that helps and please make sure to mark the solution as accepted if this information is what you needed.