instruction letter is the email that they sent for asking to send passport to them they write that it takes 6 weeks i copy this part here:
You should expect to be without your passport(s) for six weeks, so do not arrange any travel that will require your passport(s) during this period. Please note that we do not acknowledge receipt of passports. For packages signed for on receipt at the High Commission, you may be able to track receipt via the website of the courier company. If you have not heard from us after six weeks, you may contact us using the email form on our website. We will not respond to queries received after less than six weeks.
and this is their reply for inquiry Please refer to instruction letter for stated time frames.