If the chromosome no. of a cell at the beginning of a interphase is 12, what would be its chromosome no. at the end of the interphase?

by Bhaktimala
(Chennai, Madras, India)

They say there are "2n" "ploidy" before the G1 stage of inter phase; which after S phase becomes "4n" ploidy.

So what is 'n' here? is it the single chromatin thread/ the condensed bivalent/ or condensed tetravalent ?

And thus what is a Chromosome?