"I hit the first few pretty well, had a chat to Liam [Livingstone, batting partner], and I just carried on really," he told BBC Sport.
"I just remember feeling a bit of pressure on the last ball and thinking 'I have got to have a crack'.
Clark later told ESPN's cricinfo that as he faced the mental and physical challenge of clearing the fence again for the sixth time, that last shot over mid wicket probably ended up being the best of the bunch.
"It was a relief when I connected and took a lot of pressure off myself.
I didn't realise how big it was and the phone hasn't stopped ringing. It has been pretty hectic.
"It is probably never going to happen again so it is something I want to embrace.
"I don't want this to be the highlight of my career. Hopefully this is just the starting point," Clark said.
"My ultimate aim is to break into the [Lancashire] first team and my best chance is to do it in the one-day side, but this has turned a few heads and has given me a good start to the season."
Clark was brought to Wanganui for the 2009-10 season by Dilan Raj as a 19-year-old prospect from the Lancashire Academy,
"You could see there was a certain amount of talent around the young man," Raj said on Saturday.
Playing for Marist, a stress fracture in Clark's back prevented him from reaching his full potential a score of 122 in a one-day match against Wanganui High School being his best return.
He was even dropped from a competitive Hawke Cup team by then-Wanganui coach Drew Morrison that January for a lack of runs.
Wanganui Chronicle reported at the time the teenager still had his heart set on playing county cricket for Lancashire.
After Wanganui, Clark also spent a club season in Australia, where incredibly he had another chance at six sixes in an over during a game but said he "cuffed" the final shot.
The other men to belt six sixes in an over are West Indian all-rounder Sir Garfield Sobers, India's Ravi Shastri (first-class games), South African Herschelle Gibbs (ODI) and Indian's Yuvraj Singh (T20 international).