Need more character on Full Description

How should i change the limitation on Full Description, i seen i have add more words but it is not showing. Any help ?

The full description is a ‘text’ field (i.e. 16MB). My guess is that you are looking at an area in the templates where it really wants the short_description but is using the first 300 characters of the long_description instead. The long_description is only displayed in the tabbox under ‘description’.