Sorry, if this was already asked (tried to search, but results didn't show up — is this feature broken or is something wrong with my browser?), but: It's known that 10-David is lieutenant — commander of LAPD D platoon, and that 20-David through 70-David are sergeants — squad leaders. Are other callsigns just random numbers (range would start at… 10?), or are there some specific rules, for example, do element leaders have certain numbers, just like sergeants?