The numbers come closest the maximum network segment lengths in 100’s of meters. Diameters vary.
10BASE2 (or “thinwire” Ethernet or “Cheapernet”) is denotes the IEEE 802.3 physical Layer specification for a 10 Mbits/sec. data rate, baseband network with a 185-meter maximum segment length. It uses RG-58/AU stranded core coaxial cable. (see http://duxcw.com/faq/network/thinwire.htm).
10base5 (or ”thickwire” Ethernet) is the physical Layer Specification for
a 10 Mbps baseband network with a 500-meter maximum segment length. It uses double-shielded RG-11 coaxial cable.