overlay not working as i imagined

so ive tried making a furnace gui, and because there was no way of making a smelting icon such as the arrow in the furnace, i was gonna use overlays, but from what it seems its broken? as i set the base texture to the gui and its shows the inventory not only not centered but also weirdly stretched

while the normal inventory gui shows normal, and ingame the overlay is always on although i set it to show only when there is a number of items in the block's gui i dont know if its

not connected to the block or if its just broken can someone help me?

https://imgur.com/gallery/qJzN1Pk

here are some pictures

pls help