"We were expecting to be under 46 seconds so it was a good surprise to know it was a record," says Hulls of a day that offered "slight winds and nothing too extreme" in the capital.
The relay runners had an inkling their time was going to be noteworthy because some parents had their stop watches in synch before it was officially announced half an hour later.
However, the U20 world champs team won't be confirmed until next month although this week Athletics New Zealand is expected to announce a team for the Canberra Track Classic on February 20.
At the Capital Classics, Hulls, who will attend year 12 next week, finished in sixth place in the Open senior women's 100m sprint while Sheat was third.
The teenager, who competed at the World Youth Championship in Cali, Colombia, last year, has now met the qualifying standard as an individual in the 100m sprint and 4 x 100m relay for the Polish U20 world championship.