WUFI

Hello,
Does anyone know what the 'units' for Frequency of overheating are?

In a WUFI Report there is a section called Frequency of Overheating (FoO) that suggests whether or not a cooling system is needed. If FoO is a certain value, say 4%, it will say no cooling system is required. Is this saying that the house may overheat 4% of all days in a year, 4% of all days during the cooling period, something else?

Thanks

I would also like an answer to this question. I've had clients ask it and I can't find any documentation to answer it definitively.