this is my dinamic mixed config of others users:
...
$div(1411,%__bitrate%).$substr($muldiv(1411,100,%__bitrate%),2,3):1
The $substr() is only correct if the $muldiv()-result is >= 10 otherwise it's wrong because you use a static start (2) for the $subst().
This should imho be alright, you have to detect the length if the first $div.
$div(1411,%__bitrate%).$substr($muldiv(1411,1000,%__bitrate%),$add($len($div(1411,%__bitrate%)),1),4):1
Without variables hard to read and multiple computation.
BTW all in all I use this code (I only have to check it for rounding preciseness in the last digits):
1:$div(1411,%__bitrate%).$substr($muldiv(1411,1000,%__bitrate%),$add($len($div(1411,%__bitrate%)),1),4) '('$div($mul(%__bitrate%,100),1411).$substr($muldiv(%__bitrate%,10000,1411),$add($len($div($mul(%__bitrate%,100),1411)),1),4)'%)'
I rather like to have the panel to show the final compression.