In order to simplify the user interface you can select the property that will be compared with the specified threshold. Basically, three different properties are available:

Total
  Selects the total number of issues in the current build.
New
  Selects the total number of new issues in the current build with respect to the reference build. New issues will be calculated by a sophisticated algorithm that tries to track issues from build to build, even if the source code has been modified. Note that this algorithm sometimes detects outstanding warnings as new, e.g., if a source file has been refactored heavily.
Delta
  Selects the difference between the total number of issues in the current build subtracted by the total number of issues in the reference build. This is a simple subtraction, so if you have a build that adds a new warning and removes a completely different warning, then the result will be zero.

Additionally, you can select to choose all issues, or issues of a given severity only (error, high, normal or low).