Depends what system you are working with. Toyota has Intrusive and Non-Intrusive EVAP systems.
The following link on or around page 95 has a good explanation for both and how Toyota calculates P0441
https://drive.google.com/file/d/0B51-74tGswAXTGVYNUt4V3hNN00/view?resourcekey=0-ZAolYSwgK95EpjIXj-w7EA
Let me know if that helps.
Best,