If you added 3 ppm ammonia on Saturday, do another test of Wednesday, and if ammonia is till zero, add just 1 ppm ammonia. This is to keep the ammonia eaters fed while the nitrite eaters multiply without making so much nitrite that the cycle stalls.

Nitrite of 15 ppm inhibits the growth of the nitrite eaters. But our test kits don't go that high, and to get a realistic results by diluting tank water we would need pure water to dilute it with and very accurate measuring equipment.

In theory, you added 3 ppm ammonia to start the cycle, then 3 ppm on Saturday when ammonia dropped. 6 ppm in total. Since 1 ppm ammonia makes 2.7 ppm nitrite, that 6 ppm ammonia will turn into

~~12.2~~ 16.2ppm. If you add another 3 ppm, that will make another 8 ppm nitrite which will push it well over the critical 15 ppm. It won't be quite that much because there will be a few nitrite eaters, and they will increase slowly in number, but they won't make a huge impact on the nitrite level for a while yet. So we add just 1 ppm so the ammonia eaters don't go hungry, and this should not push nitrite over 15 ppm.

Edited for terrible maths. 2.7 x 6 is 16.2 not 12.2 like I said