How many days does this mean?

The third Geng day after long summer is the first day of lodging, the fourth Geng day is the first day of intermediate lodging, and the first Geng day after beginning of autumn is the first day of last lodging, with the first lodging and the last lodging each 10 day and the intermediate lodging 10 day or 20 days. Usually refers to a period of time from the first day of the initial stay to the tenth day of the final stay. Dog days are usually the hottest time of the year.