Flow Query

we have two objects one called Total Week hours and holidays.  and my current weekly hour is 40 and my working hour per day is 8.  I have created one field on another object where I want to store results>  If any holiday falls under this week the total week hour value should be (Total week hours - Hour per day) which is 32. if two holiday then value should be 24.   I have created a flow for that but its works only once. it should become 24 but its showing 32 , 32.  PLEASE ADVICE ANY IDEA