Time() class seconds math producing incorrect results?

I was doing some extendscript work with dropping in markers and had to do some Time() math.  I chose to do this with the .seconds method because tick math is a bit of a pain as it is stored as a string.

So as I was doing the math, I discovered that my results were randomly off by a frame.  Dug a little deeper and found the issue was happening with performing float math with seconds.

var demo1 = new Time();
var demo2 = new Time();

// Ticks are a form of time measurement in Adobeland.
demo1.ticks = "13558104000000";
demo2.ticks = "12743136000000";

// Setting two variables to experiment with, as named.
var demo_seconds    = new Time();
var demo_ticks      = new Time();

// Seconds math is simple and done with float.
demo_seconds.seconds = demo1.seconds + demo2.seconds;

// Ticks, for some reason, are stored as strings and need to be converted to int, then converted back to a string to store.
var demo_ticks_string   = parseInt(demo1.ticks) + parseInt(demo2.ticks);
demo_ticks.ticks        = demo_ticks_string.toString();

// This is pulling some stuff Premiere to prepare to convert time to timecode HH:MM:SS:FF
var currentSeqSettings	    = app.project.activeSequence.getSettings();

// Formatting the results of the seconds
var timeAsText_secs         = demo_seconds.getFormatted(currentSeqSettings.videoFrameRate, app.project.activeSequence.videoDisplayFormat);

// Formatting the results of the ticks
var timeAsText_ticks        = demo_ticks.getFormatted(currentSeqSettings.videoFrameRate, app.project.activeSequence.videoDisplayFormat);

// Display results in seconds
$.writeln(demo1.seconds + " + " + demo2.seconds + " = " + demo_seconds.seconds);
$.writeln(timeAsText_secs);

// Display results in in ticks
$.writeln(demo1.seconds + " + " + demo2.seconds + " = " + demo_ticks.seconds);
$.writeln(timeAsText_ticks);

Seconds Math:

53.375 + 50.1666666666667 = 103.541666666663
00:01:43:12

Ticks Math (when converted to an integer)
53.375 + 50.1666666666667 = 103.541666666667
00:01:43:13

So what's going on here?  Am I missing something obvious?  Why is the float math seemingly wrong?