increase users to display in who is new block I need to display more than 10 users in who is new block, i see the dropdown list has at max 10.

So, how can I increase it?
You have two options I see:


Recreate this block with Views - changes like that are the very sense of their existence.
Create custom module with hook_form_alter() and add numbers up to some arbitrary max you prefer. Note that it might be a performance hit that way, if block in question loads full user objects. To much and you'll eat your memory.