Why is mangling different for separate compilation?

[Atila Neves via Digitalmars-d]

On Saturday, 27 February 2016 at 03:51:00 UTC, Walter Bright 
wrote:
> On 2/26/2016 4:45 AM, Atila Neves wrote:
>> '_D3bar16__unittestL2_531FZv'
>> '_D3bar14__unittestL2_1FZv'
>
> It uses a sequence number to generate different ids for the 
> unit tests. In the former, it's the 531st unit test, the 
> latter, the first.

In both cases though, there's only one unit test. The only 
difference is how the files were compiled.

What's the number after "bar" then? It's 16 in one case and 14 in 
the other.

Atila