Maximum storage space per item of content

Hello,

I work with the 4.1 version.

I try to set a limit for the upload files of a Member Group.

I set this limit it in  Group / Member Group / Content / Maximum storage space per item of content

But it doesn’t take very well.

For example, I set 4 Mo per item of content.
It displays Max file size 4 Mo before uploading. OK.
But I succeed to upload a file of 47 Mo despite the limit. 

What's the reason ?

Thanks