A good sign indeed! I would suggest a bit of refinement however. Next time, try to determine which hole emanated from which barrel, in sequence of firing. You can do this by having an observer annotate this in a notebook (R1, L1, R2, L2, etc.). Or use my preferred method of placing a video camera (GoPro, ActionCam, or similar device) somewhere off to the side. That allows you to playback the video in order to differentiate the shots.
What you have now is a good feel for the grouping at 30 yards. Doing what I suggest above will allow you to determine the accuracy of your load from each individual barrel, and also to determine how well a specific load regulates between the two barrels. As it stands now, you don't know whether the bullets are crossing over or whether they are impacting with the left barrel on the left, and the right barrel on the right.
I would note that most doubles are regulated at a specific distance, usually 50 yards or 50 meters. But it is also useful to know where they will impact at other distances at which you personally expect to hunt. In any case, good luck with your new-to-you double rifle!
