Android Studio - Rotating device causes more and more memory to be used

I have this simple Android Studio project for testing out little code snippets. Today while I was fiddling around with some code, I noticed that each time I rotate my device, it causes the app to use more and more memory. Screenshot of the chart is as follows:

Each time I rotate the device, allocated memory increases and free memory amount decreases. When free memory hits zero, it cleans a chunk of memory, but not all. As I keep rotating device back and forth, eventually it causes more free memory made available to the app, and allocated memory keeps increasing and increasing.

This is a simple app with only single TextView and no execution code at all. No database activity, no network activity, no cursor, nothing to cause any memory leak whatsoever.

I tried to dump the java heap, but it looks all jibberish to me.

So is this the expected behavior? What is actually filling up the memory? What is going on?