Xiaomi has started rolling out Android 6.0 Marshmallow update for the Redmi Note 3 (Pro) with Snapdragon 650 in India. It was launched running Android 5.1 Lollipop starting at Rs. 9999. If you own the Indian variant of the Redmi Note 3, you will get the MIUI 18.104.22.168.MHOMIDI OTA update to Marshmallow which is a stable build. It weighs in at 1.3 GB and should be downloaded over WiFi.
The changelog doesn't say much apart from three finger screenshot along with certain bug fixes and optimizations. Although this is a stable Marshmallow build for the Redmi Note 3, it is currently being rolled out to a few users at random and once the test is complete it would be rolled out to all users.
Source: MIUI Forums