Way to check what number a player says?

So I'm trying to make a 'SetHealth' command for players, where if they type '/sethealth' and then a number after, it will make their health that number. But the problem is, I know of 0 way to reference that number. I'm trying something like:

game.Players.PlayerAdded:Connect(function(plr)
    plr.Chatted:Connect(function(msg)
        if msg == "/sethealth"..a and a == type.Number then
            local H = game.Workspace:WaitForChild(plr.Name).Humanoid
            H.Health = a
        end
    end)
end)

but it's not working /: any help?