What is the Page Memory in Webkit Timeline

I was doing some profiling for our webapp, and was trying to analyze what portion of our product takes up the most amount of memory.

I used the Memory Debugger from the Web Inspector and found that our app memory usage looks something like this:

• Page: 900MB

• Layers: 4KB

• Images: 0B

• Javascript: 170MB

From the graph, I see the page section spike when elements are being rendered, and now I wanted to look into what causes the page memory to spike. From the blog I liked, I see that the page memory is defined as

Page – All other memory. This includes engine memory related to the DOM, styles, rendering data, memory caches, system allocations, etc.

Is there a more detailed definition of what is classified as Page memory and how I can go about investigating what is taking up the memory?