The 370MB update includes some bug fixes and performance improvements, according to the official changelog. One issue in particular that many Razer Phone users have been complaining of, the multitouch bug should be addressed in the update.
Finally, Razer has decided to include the May security patch along with the update, so Razer Phone owners should be up to date with the security updates that Google releases each month. The update is deployed in waves, so if you see a notification on your phone, then you can go ahead and download it, otherwise, you'll have to wait a few more days.
source: XDA Developers