Please be assured that the product is not defective and can be used with no worries.
What you see on the surface of the plate is a "penetration”.
It is different from the cracks and scratches that occur when the piece cracks. There is no crack in the base of the pottery, so it will not leak liquid and you can use it as usual.
Even if the pottery is made of the same clay, the same glaze, and fired in the same kiln at the same time, it may or may not have penetrations due to differences in the firing temperature at the firing position in the kiln. We hope that you will enjoy our plates, considering the penetration as a unique feature of pottery.