Comparing Files with filemtime() not right

I am trying to compare two files with their modification time. But the comaprison is not working right.

I am doing it this way:

if( filemtime($fullPath.'/_mainstyle.scss') >  filemtime($fullPath.'style.css') ) {
    echo '<br/><br/><br/><br/>_mainstyle.scss '.filemtime($fullPath.'/_mainstyle.scss');
    echo '<br/>style.css '.filemtime($fullPath.'/style.css');
}

I also am outputting the filemtime, which is:

_mainstyle.scss 1532435273
style.css       1532518177

For my understanding, the Number of _mainstyle.scss is smaller than style.css but the if conditional is printing something. I also outputted a boolean of the comparison, which is true. If I reverse the comparison, nothing is put out. I don't really get why this is happening. Thank you!