Placeholders in "tabs.openWarningMultipleBranded" in Firefox

Hi.

Retrospectively (10 months late) I would like to raise an issue/question
for /tabs.openWarningMultipleBranded/ in
/browser/chrome/browser/tabbrowser.properties/, which is "You are about
to open %S tabs.  This might slow down %S while the pages are loading. 
Are you sure you want to continue?". And actually there are two:

  * The placeholders should be %1$s and %2$s.
  * The first placeholder I expect to be the number of tabs the user is
    closing. However I haven't found the expected number there. If it
    spans across multiple plural forms, we need the option to declare
    them. If not, we should know what for to use. Is the number 2, 5,
    99, any of them?

I have noticed new strings of a similar wording have appeared recently,
which already support different plural forms. If this is deprecated and
going away from Nightly, just let me know to ignore this issue.

Thank you,

-- 
Michal