How to set Site Upload Space Quota

Are you referring to space available per site or some kind of file size limit per upload?

Yes, space available per site

That same kind of control available in WordPress multisite.

I think you misunderstood a2hostingrj’s response.

If you’re not using Multisite, then there’s only one site… and, by definition, you cannot set any restriction per site (since there’s only one site).

So can you please describe what this restriction applies to? Does this relate to some plugin? Can you describe in detail the setup of your site and what you’re trying to accomplish? Can you provide some screenshots?

Or do you have a server that you’re using to host multiple WordPress sites, and want to control how much space each of those individual WordPress sites uses? (This would fall outside the control of WordPress: you’ll need some sort of server control panel to do this if you’re not very good with server administration.)

Standing by.

Or do you have a server that you’re using to host multiple WordPress sites, and want to control how much space each of those individual WordPress sites uses?

I believe this should be possible programmatically.