Diamonds checks the number of mesh nodes at calculation (elastic analysis). That means during the set up of the model, the geometry and the loads, there is no notification or warning when passing the maximum number of elements.
What you exactly can do with 2500 mesh nodes highly depends on the choosen mesh size. Below are some example structures with 2400-2500 mesh nodes and an acceptable mesh (not too fine and not too course).
Bar structures
For bar structures, 2500 mesh nodes correspond with approximately 300 bars.
2D Bars license
3D Bars license
Plate structures
For plate structure, there is no equivalent in number of plates. It depens on size of the plates and the choosen mesh.
2D Slabs license
3D Structures license 
In your own Diamonds model
In your own Diamonds model, the number of mesh nodes is displayed at the elastic analysis.
In the image below, there are 221 mesh nodes.
