Correct Server-Timing headers

Hi
I am confused a little, from spec I see that header should look like:

Server-Timing: cache;desc="Cache Read";dur=23.2

Server-Timing: ssr;desc="Server Side Rendering";dur=60

But in fact this headers will not show time in a Chrome, only two lines
'desc'.
If I will use header this way:

Server-Timing: DO_NOT_MATTER=60; desc="SSR";


I will get `SSR: 60ms` in the Chrome Developer Tools. But why DO_NOT_MATTER
do not matter?
And it's kinda differ from spec.

May you please clarify how I should use this header.
With all Best Regards.