Im trying to get this to run every 300ms but it dosent run at all

var gametick = new System.Threading.Timer((e) =>
        {
          //stuff
        }, null, 0, TimeSpan.FromMinutes(Convert.ToDouble(300).miliseconds);

I dont know what to try but i am expecting to use this to add gravity to my charater so every 300 ms he goes down one block but it didnt effect the game at all