Dear Maina,
It can be both. A mind which easily imagines and visualizes can also easily see things in meditation which appear to be real but are only imagination. If however you are in a deep meditative state, calm and uplifted, it can also be a true vision. In that case don’t think too much about its meaning but rather absorb yourself in that vision. I can only guess what its meaning is (cosmic completeness), but you can intuit it directly, which is more important.
If however your honest discernment tells you that probably it is fruit of your imagination, don’t concentrate on it at all but practice an effective meditation technique.
All the best,
Jayadev