1955 Wheat Penny With Unsure Errors On Reverse

Well this one is a die break. After the die crack or chip enlarges, it eventually is called a die break. When the edge of the die breaks away then it is called a Cud.

When the die splits and breaks off it is called a split die:

Before this happens you see die cracks/breaks across the center of the coins.

Also there are rim Cuds:

But when the term Cud is used, the metal will be higher than the rim:

Seeing will help keep this in mind. You might do a screen shot of this area to record all this information and images for your personal education files?

The reverse die first had a die crack. Then the chips started falling out of the die. Eventually it progressed into die break. (because of the size of the void on the die) Here is a different example at a different angle:

Note how the void on the die allow the metal to form to that height on the 'T'?
Just the die being kept in use and not retired yet. Happens a lot on the 1950's Wheat cent.