attempt to compare string and number?

Recently I started making my own Ban System for the sake of learning and having a Ban System. Everything went out perfectly fine until I tried coding the part if the player's Ban is greater than the given length e.g(1 Day, 3 Days, 1 Week). But I keep getting confused on this attempt to compare string and number error.

Line 30 is

if isBanned.BanStart - os.time() > isBanned.Length then

if any of you are wondering.

local function IsPlayerBanned(player)
	local playerKey = "Player_" .. player.UserId
	
	local isBanned
	local success, errormessage = pcall(function()
		isBanned = HttpService:JSONDecode(BanDataStore:GetAsync(playerKey))
	end)

	if success then
		if isBanned.BanStart - os.time() > isBanned.Length then
			BanDataStore:RemoveAsync(playerKey)
		else
			player:Kick(string.format("\nYou've been banned by " .. isBanned.Admin .. "\nReason: " .. isBanned.Reason .. "\n\nBanned until: " .. os.date("%B %d %X", os.time() + isBanned.Length)))
		end
	end
end