PIDS11 — Question or issue regarding collaboration diagrams

> I think that this example on page 3-127 is wrong or terribly misleading.
> [x < 0] 4: invert (x, color) – conditional Message
>
> If I read right, condition-clause is supposed to follow the sequence number.
> So the correct example would be:
> 4 [x < 0] : invert (x, color) – conditional Message.
>
> To me, this is a guarded message
> [x < 0] 4: invert (x, color) – guarded Message