Best slot
The best ad position this listing held in this slot group.
The single best position this listing reached in the selected slot group during the period. The counting runs across the whole search page, so the best possible number differs per group: in Top of Search it is #1, but in Rest of Search the count continues after the top block — #5 is the very top of that shelf, not a weak spot. In Brand collection and Product carousels the number is the card position inside the carousel, so #1 means the first card. Brand video has a single hero slot, always #1.
Lower is better — but judge it against the group's own scale, not against 1.