See Product Limits 

For 3.6:

 https://docs.delltechnologies.com/bundle/PF_KNOW_36/page/GUID-480ABD0F-4DB5-4F07-9EC4-4779CBF5E9A4.html

Hi Peter,  
Max allowed over-provisioning=20.
ie can create volumes 20 time the size of your physical capacity (thin volumes).

So if you have 10TB,then you can  create volumes up to 200TB thin volumes.

I will look for some official documentation for you.

Gearóid

I think over subscribe storage size should be always avoided.  Why you present a 200TB volume to a server when the underlying storage can only store 20TB of data?    It doesn't give you any advantage other than when you fill the disk with 19.9 TB data on the server but won't get the low disk space warning.  In fact, it will give you a deadly problem if you store an Exchange or SQL database on an oversubscribed volume when it reaches the physical limit in the underlying storage.