How to add tables in DataStore without overwriting other tables in the DataStore?

So I have been wondering if it is possible to add tables in DataStores. I already used SetAsync to set the first table in the DataStore, which is myTb. I removed SetAsync after that. Here is my code that I tried out:

local dataStore = game:GetService("DataStoreService")
local gds = dataStore:GetDataStore("gds")

local myTb = {{sName = "server", sNum = math.random(1, 9999999), sAvail = true, playersInQueue = {}}}
local key = "figure"

local f = gds:GetAsync(key)
local x = f[1]

for i, v in pairs(f) do
	print(i, v)
end

for i, v in pairs(x) do
	print(i, v)
end

local function updateAvailability(currentValue)
	local serverTable = currentValue[1]
	local serverName = serverTable["sName"]
	local serverNumber = serverTable["sNum"]
	local serverAvail = serverTable["sAvail"]
	local plrsInQ = serverTable["playersInQueue"]
	
	local updateServerAvailability = {{sName = serverName, sNum = serverNumber, sAvail = false, playersInQueue = plrsInQ}}
	return table.insert(f, updateServerAvailability)
end

local success, newVal = pcall(function()
	gds:UpdateAsync(key, updateAvailability)
end)

if success then
	wait(1)
	local log = gds:GetAsync(key)
	print(#log)
end

At line 36, I am expecting the number of tables in the DataStore table will be two, however, the output says it is only one. Did I make any mistakes in my code?