local guid = UnitGUID("target")
local unitType, _, _, _, _, _, spawnUID = strsplit("-", guid)

if unitType == "Pet" then
    local petUID = string.sub(spawnUID, 3)
    local spawnIndex = tonumber(string.sub(spawnUID, 1, 2), 16)

    print(guid)
    print("Unique Pet ID:", petUID)
    print("Spawn index:", spawnIndex)
end

> "Pet-0-4234-0-6610-165189-0202F859E9"
> "Unique Pet ID:", "02F859E9"
> "Spawn index:", 2

Hunter | Dash | 30 | 1 | 23100
Hunter | Dash | 40 | 2 | 23111
Hunter | Dash | 50 | 3 | 23112

Hunter | Growl | 1 | 1 | 1853
Hunter | Growl | 10 | 2 | 14922
Hunter | Growl | 20 | 3 | 14923
Hunter | Growl | 30 | 4 | 14924
Hunter | Growl | 40 | 5 | 14925
Hunter | Growl | 50 | 6 | 14926
Hunter | Growl | 60 | 7 | 14927
Hunter | Growl | 70 | 8 | 27344

					-- Loop through all of the group members and add their pets and pet's class to the maps.
				local unitPrefix = IsInRaid() and "raidpet" or "partypet"
				local numGroupMembers = GetNumGroupMembers()
				for i = 1, numGroupMembers do
					local unitID = unitPrefix .. i
					if (UnitExists(unitID)) then
						-- XXX: This call is returning nil for party members in certain circumstances - need to debug further.
						local guid = UnitGUID(unitID)
						if (guid ~= nil) then
							petMap[guid] = unitID
							if (not classMap[guid]) then _, classMap[guid] = UnitClass(unitID) end
							classTimes[guid] = nil
						end
					end
				end -- Loop through group members
				-- Add the player's pet and its class if there is one. Treat vehicles as the player instead of a pet.
				if (petName) then
					local unitID = "pet"
					local guid = UnitGUID(unitID)
					if (guid == UnitGUID("vehicle")) then unitID = "player" end
					petMap[guid] = unitID
					if (not classMap[guid]) then _, classMap[guid] = UnitClass(unitID) end
					classTimes[guid] = nil
				end				
				```