for($i=0;$i<=15120;$i+=504){
echo ($i/60/8.4) . " - " .floor($i/60/8.4)."<br>";
}
Result (i make ** at problem) :
0 - 0
1 - 1
2 - 2
3 - 3
4 - 4
5 - 5
6 - 6
7 - 6
8 - 8
9 - 8
10 - 10
11 - 11
12 - 12
13 - 13
14 - 13
15 - 15
16 - 16
17 - 17
18 - 17
etc...
At start i think i apply "Floo" at all calculation but (for line "7-6") also $i = 3528 :
3528 / 60 = 58,8 == Floor ==> 58 / 8 = 7.25
floor of 7.25 =/= 6
it because of PHPs floating point precision
so your 8th calculation for example will not return 7, but something like 6.9999999999999999999999999999
as this is a double, it will be rounded to 7 on output, try this out:
$x = 6.9999999999999999999999999999999999999999999999999999999;
echo $x;
when you use floor() it will (correctly) round it down to 6