The max limit of a signature is 600 pixels wide by 100 pixels tall (:
Seems like you got the formatting down, but, if you need to know, it's
! [] (link)
All without spaces in between, and the [] are two brackets
EDIT: Also, yeah, it's the wrong area, but no worries. So long as it's not getting bumped, it should be fine. They may delete it later on, as well, but don't know. May just lock.