I have made ceramics for years.

All ceramics when made from wet clay dried throughly then fired into greenware shrinks.

Kilns need temperatures of 2,500 degrees Fahrenheit for 24 hours to turn the clay into ceramic if the temperatures get too high or too low the ceramic will explode or melt. Then after it is fired it has to cool gradually.

Then to increase the strength of the ceramic glaze is added to reinforce the fragile greenware. Glaze is extremely toxic too until fired.

The only way to know to counteract the shrinking is to make a small ruler with measurements and fire it into greenware.then find the percentage of how much it shrinks with a caliper or ruler.