1) Welcome to the Party!
2) As you are obviously new here, I have some suggestions to help us all help you:
When you post, please post your entire configuration including (but not limited to) your installation method (7.X.X?) and vicidial version with build (VERSION: 2.X-XXXx ... BUILD: #####-####).
This IS a requirement for posting along with reading the stickies (at the top of each forum) and the manager's manual (available on EFLO.net, both free and paid versions)
You should also post: Asterisk version, telephony hardware (model number is helpful here), cluster information if you have one, and whether any other software is installed in the box. If your installation method is "manual/from scratch" you must post your operating system with version (and the .iso version from which you installed your original operating system) plus a link to the installation instructions you used. If your installation is "Hosted" list the site name of the host.
If this is a "Cloud" or "Virtual" server, please note the technology involved along with the version of that techology (ie: VMware Server Version 2.0.2). If it is not, merely stating the Motherboard model # and CPU would be helpful.
Similar to This:
Vicibox X.X from .iso | Vicidial X.X.X-XXX Build XXXXXX-XXXX | Asterisk X.X.X | Single Server | No Digium/Sangoma Hardware | No Extra Software After Installation | Intel DG35EC | Core2Quad Q6600
3) Statuses are listed in Admin->System Statuses AND in each campaign's top menu (Choose a Campaign -> Detail View Top Menu -> Statuses). Note that if a status is deleted from either of these locations, that does not delete any previously recorded statuses. IE: If someone created a "T" status and later deleted that status, then there will be no linked "Description" or "Category" for that status. But if you create one now, it will "link up" to any statuses that already exist.
4) If your system has 3rd party software or customizations (such as API access) running, it's entirely possible that this status does not exist, but someone has been creating leads with it. You would have to ask whoever customized the system if "t" has a meaning of which you should be aware.
Happy Hunting!