The direction a planet is moving (prograde or retrograde) is really not significant when discussing this subject. Their position at a certain time - like a snapshot is far more important.
Knowing Mercury's position is enough- it doesnt matter which direction its going in the night sky.
Whether the exact position of Saturn was a bit in front, or a bit behind the swallow is also unimportant. The fact that it is close is enough. It is only in that part of the sky once every 29.4 years.
In 588 , Saturn wasnt anywhere near the swallow. This stuff is not hard to understand.
JW's seem to be the only group determined to question the credibility and squeeze out answers from VAT 4956 that just arent there.