The delta value is seen throughout the Growblocks platform.
The delta refers to the difference between your plan goal and your actuals/projection. A delta can be positive or negative.
The delta can be seen in various places across your engine. See an example here in the details view.
In your new business dashboard the delta is shown across the different metrics seen, and shows the difference between the projection and the plan goal at the end of the period you have selected.
The performance trend is comparing the delta between projection and plan goal today vs X weeks ago. You can choose how many weeks ago (up to 12 weeks) you are comparing to in the selector on the top right.
For more details on the delta calculation, along with the performance trend (delta movement) see the diagram below.