What does the blue and green colors mean in xcode memory debugger

Question

1. What does the blue and green boxes indicate?
2. Does the number in the bracket show objects created and destroyed over the period before invoking the debugger? Or are they objects still alive in the memory?

I can't seem to find any explanation on the apple website or WWDC videoes (or maybe I missed it.)

Answer 1

Half answer:

2. Its the number of objects currently alive in memory. Based on tests I ran myself.