Kentucky Derby Day 1944

The transcript describes a major horse racing event attended by 60,000 people. Attendees arrive by trolleys and cars, filling the venue hours before the event. While few celebrities are present, the betting scene is lively, with Stir Up #6 being a favorite. The race features 16 three-year-old horses, with some bettors choosing Pensive, a chestnut colt with 7 to 1 odds.

What is the betting situation described in the text?

What is the significance of the field of 16 three-year-olds mentioned in the text?