fix: [0km] display resident memory in ``vps-stats``

bin/0km

@@ -1639,7 +1639,7 @@ graph:def:c.memory() {
         fi
         container="${container//\'/}"
         container="${container//@/\\@}"
-        echo -n "  ${rrdfetch_cmd} u 1:((\$3 - \$2)/1000000000) w lines title '${container//_/\\_}'"
+        echo -n "  ${rrdfetch_cmd} u 1:(\$3/(1000*1000*1000)) w lines title '${container//_/\\_}'"
     done
     echo
 }