Contact field is showing as a list/record field instead of a drop-down select field

The following are reasons on why the Contact field from any record would show as a list/record even when the Maximum Entries in Dropdowns = 500 (under Home > Set Preferences).

1. There is a limit of 50,000 entities. If this limit is reached, the system will use a pop-up select instead of a dropdown regardless of customer's preference due to performance reasons.

2. Another limit is if any customer record is linked to more than 500 contact records, then all Contact fields will show as a pop-up select field (List field).