Ok.
So my girl usually goes into heat for 4wks instead of the usual 21 days. Everytime it has been exactly 28days every 6month.
Well we have decided to breed her this cycle(first time).
We did not do progesterone testing, instead we went off on her and the males behaviour together and watching her blood.  started heat on 18th July, mated 1st & 3rd of Aug. Blood thinned to very light colour from 31st July. So 8th of August bleeding stopped completely, today 9th I noticed a small amount of brown blood where she had been sitting, wiped her vulva and there was a little there. So I was on the case with the vet immediately as I was worried for pyo or other infection. Totally fine, she's dandy. Just some old blood and she's had none after that little bit. I would have noticed if there was more as im watch her like a hawk.
Anyway the point of the post.. I have read that a bitch will continue her season after mating wether she was pregnant or not? Little bit confused as she is usually 28days but she's stopped early. Any ideas why she has stopped early. Thanks

Yes to still being in season to the normal end of the season, which is why you still have to keep her confined.   But if any of mine, mated, ended a bit early, I took it as a good sign.

Mine continue on through but a friend in another breed hers stop a few days after mating

Mine stopped bleeding just after mating too. Mated day 11 & 13. Stopped bleeding day 15. Her other seasons were all 21-24days. I'm hoping it's a good sign she's taken but time will tell.

As said with mine but just be aware, you should still confine until the normal end of her season, just in case!!