What is Solver settings?
Settings that control how finely and how accurately the numerical solver works. The defaults are fine for most uses.
Tighter tolerances give more accurate results but take longer. They are sometimes adjusted when a calculation does not converge.
Like a map: a finer scale is more accurate but takes longer to draw.
Change them under “Solver settings” on each block. They are recorded with the result, and different settings count as a different calculation.
rtol is the relative tolerance and atol the absolute tolerance. For the PFR, n_steps sets the maximum integration step and the resolution of the reported profiles.