Clarity gives you 2 methods to calculate the 7 key numbers:
1. annualised - extrapolating the figures for a period of less than 12 months (say 9 months) to that of a full year (12 months) comparing that to the previous financial year - this works fine for the majority of businesses, especially when the finalised month is the year end.
2. rolling 12 months - using the finalised month's figures plus the prior 11 months (12 months in total) to calculate the key numbers and comparing the the prior rolling 12 months - this can be better for businesses that are seasonal or that have long term contract revenue.
Annualised is the default calculation. You can change the calculation method in Settings for your company.
If you don't have at least 12 months worth of data then you'll need to use annualised. If you don't have at least 24 months worth of data then no comparatives will be shown with the key numbers when using the 12 month rolling calculation method.