The recipe below is meant for an estimate of 5 complete pieces of agar agar jelly mooncakes, with some extra.
You can free to change the amount of sugar and coconut milk to water proportions as you desired.
The standard rule of thumb is 1 pack of agar agar powder (10g) is to be mixed with 1000ml of water. If you prefer it firmer, you could reduce the water by 100ml or reduce 1 teaspoon of powder from the 10g pack.
And if coconut milk is added, reduce that amount from the water accordingly (For example, if 250ml of coconut milk is added, reduce the water to 750ml for a same pack of 10g of agar agar powder.)
How much coconut milk is to be used depends on individual’s preferences as well. You are free to replace it with fresh milk or soya bean or even if all are not preferred, just water will do also !