Q: intel iris

Hi, I have macbook pro 13 retina. My memory of my intel iris change from 1536 mb to 1024 mb. I am really worried. It is normal?

MacBook Pro (Retina, 13-inch, Late 2013)

Processer:   2.6 GHz Intel Core i5

Memory: 8 GB 1600 MHz DDR3

Graphics : Intel Iris 1024 MB

Storage : 256 SSD

MacBook Pro, OS X Mavericks (10.9.5)