Oyisa Marhasi notched six goals in the first half, and was then promptly taken off by coach Simphiwe Dludlu.
Tiffany Kortjie, one of two changes that South Africa made at the break, netted within two minutes of coming on and went on to score six of her own inside 30 minutes at an average of one goal every five minutes.
Captain Jessica Wade was the first to get to a hat-trick, doing so inside the opening 18 minutes and Nabeelah Grant and Sonika Mzingeli also got a trio of goals.
Seychelles were playing their inaugural game at under-17 level and entering the southern African championship for the first time.
“We knew it would it very difficult because we haven’t had women’s football in the Seychelles for the last five years,” said their coach Vivian Both afterwards.
“We have only been training (together) for two and a half months. It’s the first competition we have taken part in.
“It’s good to be in this kind of situation so that when they (the team) go back home they will know that if they want to be at a certain level they have to train hard.”
In contrast, it was a spectacular performance by South Africa and one to remember for coach Simphiwe Dludlu.
“Today is my birthday so they (the team) decided they were going to shower me with a bit more gifts.
“It was a great game for us and I commend my girls for their discipline, sticking to the game plan and wanting to do things rights. They put the work they had done in training into practice in a game situation,” added the South Africa coach.
“Nobody wants to have 28 goals scored against them but you have to start somewhere. It’s a learning curve for them and they can now see there are women out there, who are their own age who are playing good football.”
Ghana’s 12-0 win over Malawi in October, 1962 is generally held to be the biggest winning margin in the men’s game on the continent, although there are no records on the largest winning margins held by either Fifa or the Confederation of African football (Caf).
At junior level, the previous highest winning margin was also held by south Africa’s under-17 women who beat Botswana 13-0 in a World Cup qualifier in 2009.
The record score in any international is a 31-0 victory for Australia over American Samoa in World Cup qualification in 2001, including 13 goals by Archie Thompson.