How to Find the right U Count Value for SurfaceFromPoints (SrfGrid)

Hello, I am trying to use the mosquito plug in to run a water level simulation and it needs a surface. I have my terrain as a mesh so I am using DeMesh and SurfaceFromPoints. The SurfaceFromPoints (SrfGrid) needs a U value / U count that I have to enter with a number slider. But it gives an error to me "UCount Value is not valid for this amount of points.
I have a total number of 3466 points in my mesh and I used this before with a similar terrain and it was easy to try and found the right U Count value, it worked before. But in this one I cannot find the right UCountValue at all.

I dont know is spesifically there is only 2 dividers of this number which is 2 and 1733.

I hope someone can help me here, thank you in advance.

PS: If you need an explanation for the attachments. I have 2 terrains inside, one is the existing and the other is the proposal. I need to use the plugin for both to see the comparison. The excluded parts in the model are the river course.
before after grasshoper (278.0 KB)
Model_Agriculture_before after.3dm (3.9 MB)

surface from points wants a consistent grid of points to work correctly, I would suggest something like → project a grid of points on the original mesh (where the river course was not cut out) → build the surface with SurfaceFromPoints → only at this point cut-out the portion of surface where the river is, by projecting the boundary curve of the river on the surface that was just created

something like this, didn’t project and cut-out the river, just stopped after the flow sim

before after grasshoper (190.7 KB)