This meditation necklace is part of a purification process. During the purification, visions and thoughts come. It is just like when you are washing clothes; you see the dirt coming out into the water.
In the same way, when the mind is going through the purification, then thoughts and visions occur. But they occur only for a moment, and then they disappear.
That is why we need to be careful in this regard, because if you are watching, then the mind can very easily get involved in the thought, and if it gets involved it can further acquire new imprints.
This re-acquiring is so subtle. This is why it is so important not to analyze thoughts during meditation, and this is also why the total cleansing of the mind takes time.