Why are these estimates different?

[ImTorey]

If I use this link to determine how fast a 15 GB file will download on the T3/DS3 Connection my estimate and the calculators are different anyone care to explain?

is my math wrong?

45Mbps / 8 = 5.625

15360 / 5.625 = 45 Minutes and 31 Seconds?

The calculator gets 48 Minutes exactly.

 

[office politics]

here's the logic they use

note - (((factor * filesize)*1024)*8) / kps[x]; **kps[x] is the download speed

var sizenum = 12;
kps = new Array(sizenum);
kps[1] = "14400";
kps[2] = "28800";
kps[3] = "33600";
kps[4] = "56000";
kps[5] = "64000";
kps[6] = "128000";
kps[7] = "640000";
kps[8] = "1544000";
kps[9] = "44736000";
kps[10] = "155200000";
kps[11] = "622080000";
kps[12] = "2488000000";
 
function calc(factor) {
        if ((document.grid.size.value == null) || (document.grid.size.length == 0)) {
                document.grid.size.value = "";
                alert("Please enter a file size");
        };
        var filesize = parseFloat(document.grid.size.value);
        for (x = 1; x <= sizenum; x++) {
                var filetime = (((factor * filesize)*1024)*8) / kps[x];
 
                hourmod = filetime % 3600;
                hour = Math.floor(filetime / 3600);
                minute = Math.floor(hourmod / 60);
                second = Math.floor(filetime % 60);
                if (hour <= 9)
                document.grid[x + "h"].value = "0" + hour;
                                                                                                                                else
                document.grid[x + "h"].value = hour;
                                                                                                                                if (minute <= 9)
                document.grid[x + "m"].value = "0" + minute;
                                                                                                                                else
                document.grid[x + "m"].value = minute;
                if (second <= 9)
                        document.grid[x + "s"].value = "0" + second;
                else
                document.grid[x + "s"].value = second;
        };

 

[ImTorey]

Thank you