Thanks, that one with missing in my collection. On a general note. To control the heat in the potjie is important. If you puss too much heat from below, the meat on the ground may get dry, stick or even get charred a bit. Letting the charcoal have some distance from the potjie may help.
the ratio I've come to use is that 1 briquette imparts 5-10 degrees, (usually for me i say 10) so 12 below and 24 above roughly 360 degrees. usually my minimum is 8 below 16 on top. don't forget to rotate the lid 1/4 turn every 10-15 min and the pot 1/4 turn in the opposite direction every 10-15 min. to evenly distribute the charcoals heat.I think there is a chart on the lodge site that will tell you how many charcoal lumps to put on top and below your oven. Like 6 below and 12 on top gives you 300 deg. heat for a 10" oven. If I remember right it has a chart that covers 8, 10, 12, & 14 " ovens.