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 and vicidial version with 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 "from scratch" you must post your operating system and should also post the .iso version from which you installed your original operating system. 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) -4 Lower means that any calls with -3 through zero or anything higher than zero will take precendence and get to an agent before those -4 priority calls. Since outbound calls are Priority Zero, there will never be a call sent to an agent of -4 as long as there are outbound calls waiting to get to agents. Perhaps setting it to -4 without knowing this was a bad idea. PS: Campaign call priority is ignored when loading leads into the hopper. It is hard-coded as Zero instead of whatever you set the campaign to.
4) Next time: Test any change like this yourself by calling in before assuming it will work as you expect. Open Source Software does not follow "Your Rules" or "Common Sense" ... it runs on the whim of whomever pays for that bit of code to be written. And if you make a change that steps outside the expected boundaries you can get a bad surprise. And here's the fun part: There is no way to know where those expected boundaries are without Testing. So ... always test.