The initial MIUI 10 update was based on version 8.5.31 and a week later v8.6.6 was released. Today, Xiaomi has another beta update for the Redmi Note 5 Pro that installs version 8.6.11. Being a nightly update, there isn’t much the new software brings forth other than multiple bug fixes and optimizations that improve system performance.
Since the current MIUI 10 is a beta version, such minor updates are necessary and carry significant importance as far as ensuring smoothing performance is concerned, so make sure you grab the new version 8.6.11 once the download notification shows up.
BTW, if you need help with installation of the MIUI 10 on Redmi Note 5 Pro, or any other device, check out this page regarding how to install MIUI 10 update.