Depending on how much memory your GPU has access to the poolsize can vary (I have 6GB but choose to dedicate 4GB). I prefer adding it to the defaultengine.ini file as opposed to adding it to via the Console each session.
Add to DefaultEngine.ini
[/Script/Engine.RendererSettings]
r.GenerateMeshDistanceFields=True
r.Streaming.UseFixedPoolsize=True
r.Streaming.PoolSize 4000
I found the information in this link Increase Non-Streaming Texture Pool Size? - World Creation - Unreal Engine Forums
Hope it helps.