`a` in the interface documentation, you can specify the left upper corner of
the wanted submatrix for the operation by setting `ar` for the row and `ac`
for the column (1 by default). A vector `y` would have an extra optional
-parameter `ofsy` (also 1 by default).
+parameter `ofsy` (also 1 by default). Parameters like `m` or `n` typically
+specify the numbers of rows or columns.
### Printing vectors and matrices