Hi Sean 👋
It's nice to see you here, I think we've spoken like a couple times on +42400. How are you?
+42460 provides support for SEA users i.e. Malaysia, Singapore, Indonesia and Brunei whereas +42400 provides support (mainly) in English for all other countries without a regional support account. You can find a list of Telegram Support numbers here:
http://telegramgeeks.com/2016/03/contacting-telegram-support/
I can't tell you the exact team size but it's usually between 10 ~ 20. Some of the team members have access to more than one support account so it's hard to keep track of the team but we are a smaller team as compared to other support teams.
(PS: The website above is a fan page and not powered by Telegram.)