A chip turns many local readouts into indexed positions. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
A chip has addressable positions
The schematic chip has 5 rows and 4 columns.
rows=5,cols=4
Address count is exact
The grid contains 20 addresses. The cloning or sequencing chemistry is outside this count model.