What does this line "?2irtgd" belong to?

Question

css

In my project, I use mixins to generate fonts so as not to write the paths with pens, but when Icomoon generates (the generation occurs when creating a font on the site), the following line appears "? 2irtgd". Each new generation has a different content. Please tell me if it makes sense to ignore them, and if not, how to write a mixin so that when importing fonts, it would find this line "? 2irtgd".
I know a joke about IE, but I didn't find anything else.
About declaration for IE
First, there are two of them. The first line (src: url(journal-webfont.eot);) is for IE9. The second is IE6-8. (journal-webfont.eot?#iefix) such a tricky entry is needed to fix a potential bug in IE that can clumsily process src. IE9 understands WOFF well, so if you include separate styles for IE6-8, you can leave only one line and at the same time you can remove the bug fix and format.

@font-face {
  font-family: 'Icomoon';
  src:  url('fonts/Icomoon.eot?2irtgd');
  src:  url('fonts/Icomoon.eot?2irtgd#iefix') format('embedded-opentype'),
    url('fonts/Icomoon.ttf?2irtgd') format('truetype'),
    url('fonts/Icomoon.woff?2irtgd') format('woff'),
    url('fonts/Icomoon.svg?2irtgd#Icomoon') format('svg');
  font-weight: normal;
  font-style: normal;
}

[class^="icon-"], [class*=" icon-"] {
  /* use !important to prevent issues with browser extensions that change fonts */
  font-family: 'Icomoon' !important;
  speak: none;
  font-style: normal;
  font-weight: normal;
  font-variant: normal;
  text-transform: none;
  line-height: 1;

  /* Better Font Rendering =========== */
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}