How to make an rxjs marble sync grouping only take up one frame

Question

According to https://github.com/ReactiveX/rxjs/blob/master/doc/writing-marble-tests.md

'--(abc)-|': on frame 20, emit a, b, and c, then on frame 80 complete

So how do I represent "on frame 20, emit a, b, and c, then on frame 40 complete.

Ie how can I stop the sync group itself taking up frames?

Answer 1

cartant has answered this question in his comment.

There's no way to do it - sync groups will always take up extra frames even though all members occur in the frame of the opening bracket.