She lined up against Botswana’s Amantle Montsho, and South African 400m hurdles ace Wenda Nel on a cool autumn evening.
"I didn't really target a time, it was more about me enjoying myself, but the time is amazing, maybe in future I will try and go faster," Semenya saaid.
"I obviously have respect for them, they are sprinters, soecialising more in 400m and 400m hurldes so for me it was more about pacing myself."
Heide Seyerling-Quinn holds the South African 300m record with a time of 37.02secs she posted in Sydney in 2000.
Female hammer throw prospect Letitia Janse van Vuuren improved the national record she set last month by almost three metres.
Janse van Vuuren launched a best heave of 63.82m in the home of hammer-throw legend Chris Harmse.
The record-breaking throw comes a month after she broke Annemie Smith's previous record.
"It felt good, the first time I didn't expect it but this time I felt better prepared and I knew I coukd do it," said Janse van Vuuren, who trains with Harmse.
"I had a good few weeks of training before this."
The 20-year-old Janse van Vuuren trains under the tutelage of Basie Koen at the hammer academy in Sasolburg.
Although Janse van Vuuren has shown drastic improvement over the last few months, she did not allow her imagination to run away with her.