q05_cell_abundance_w_sf is the absolute cell abundance - the expected number of cells that express every reference cell type signature. So these values range from 0 to arbitrary positive values - there is no maximum number of cells per spot specified anywhere in the model. The expected cell abundance N_cells_per_location is the average total number of cells expected in the tissue. This value is used to guide (prior) cell abundance estimation - not a hard constraint.
In general, the statement “relative cell type abundance” doesn’t have a clear meaning. You need to specify what exactly is computed and presented - eg how the values are normalised. For example, relative cell abundance could mean normalised by tissue area or normalised by volume - a number we present when analysing data types with variable location sizes - such as Nanostring data.