Double minus in calc css

[taime]

Bug Report

There are double minus in css file (--1px)

Steps

Download https://cdn.jsdelivr.net/npm/[email protected]/dist/semantic.css

Expected Result

 .ui.attached.steps {
   width: calc(100% + (1px * 2)) !important;
   margin: 0em -1px 0;
   max-width: calc(100% + (1px * 2));
   border-radius: 0.28571429rem 0.28571429rem 0em 0em;
 }

Actual Result

 .ui.attached.steps {
   width: calc(100% + 2px) !important;
   margin: 0em -1px 0;
   max-width: calc(100% + 2px);
   border-radius: 0.28571429rem 0.28571429rem 0em 0em;
 }

Version

2.4.2

There are also some places with double minus like here (--1px)
I really think this is mistake. It it's not, please tell me what does it mean ?