aridic in subgroup

please explain by an example that how can we determine 6/10 of cumulative days? one year is 365 days . is 6/10 of 365 days ?? or if 190 days are as cumulative dry .so we should determine 6/10 of 190 days ?how do we calculate 6/10/?

according to definition of aridic in keys to.....:

all parts for six-tenths or more of the cumulative
days per year when the soil temperature at a depth of 50
cm below the soil surface is higher than 5 oC;