Increase number of characters in text field

[ruler68jg]

I am getting this message :

1. The text that you have entered is too long (11615 characters). Please shorten it to 10000 characters long.

I want to increase the number of characters, could you kindly advise me where I can get a hold of the setting

kind regards
ruler68jg

[Zachery]

AdminCP > vBulletin Options > Help Message Posting and Editing Options > Maximum Characters Per Post