IMHO this is the best use of the Brewing Sugar provided in the equipment cartons. Coopers would be better served by supplying a packet of Brew Enhancer 2, as it makes better beer and would 'hook' the brewer into continuing.
I just bought by brother in law an equipment kit and I added a packet of dme so his first brew would be better.
I use Coopers Brew Enhancer 2 for priming at a rate of about 220g for a 23 litre batch, yes it costs a little more than sugar, but it's not always about the cost, it's about making the best beer you can.
I'd use about 15% more Brewing Sugar than if you were using straight sugar. If using a teaspoon, I'd make it a heaped teaspoon and you should be right.