Adobe Acrobat Forms : Add a specific number at specific interval

I am trying to add a particular number at regular intervals

I have difference between 2 dates  in hours   

so  for first 24 hours  result 1  ,

even more than a minute to 24 hours >> result 1+.5 = 1.5 ,

then again even more than a minute  to next 8 hours  >> result 1.5 + .5 = 2

then again even more than a minute to next 16 hours  >> result 2 + .5 = 2.5

then again even more than a minute to next 8 hours >> result 2.5 + .5 = 3

then again even more than a minute to next 16 hours >. result  3 + .5 = 3.5   and so on.

In short .5 to be added after 24 hours for at every more than 8 hours & 16 hours 

I am using the below script  but not able to achieve the above :

var miles = this.getField("minutes").value; //difference between days in minutes

var hrs = Math.floor(miles/(60*24));  //capturing the hours part
var min = miles%60 //capturing the remainder minutes

if(hrs == "0" && min > 0){event.value =1}
else if (hrs >0 && min >0) {event.value = hrs + ".5"}
else if (hrs > 0 && min == "0"){event.value = hrs}