itch.io

First put this in its own script,

function inventory_get_qty(item_id) {
      for(var c = 0; c < global.inventory_items; c++){
          if(global.inventory_item[c] == item_id){
              return global.inventory_qty[c];
          }
      }
      return 0;
 }

Then you can draw the quantity with,

draw_text(0, 0,tsprintf("POTION %", inventory_get_qty(item_POTION)))