R&D pre-notification form for extended periods

Hi I have a period of account 28/08/22 to 28/02/24 (18 calendar months), but when entering this into the per-notification form I receive an error that it cannot be longer than 18 months Is there a fix? should i state the period is 29/08/22 - 28/02/24 just to be able to enter it?

Hi,
Guidance in relation to filing a pre notification form longer than 12 months can be found at What information you will need.
Thank you.