I think you are asking about what is the capacity of the bacteria colonies to deal with increases of waste production. Each individual bacteria's processing amount is very small, but cumulatively there is a maximum amount that can be dealt with and a minimum sustaining amount.
When you are first starting out you may only have 100 bacteria and just for example lets say those 100 can deal with 100 units of waste maximum, and will not decline in number if they get at least 25 units of waste per that 100 bacteria. More than 25 means growth in number can begin and less means die off. Max intake of 1 unit of waste per bacteria just means max growth possible. For our example lets say growth at max is that they double every day. The numbers differ from this and reality is a little more complex than this, but we'll use this to explain.
Once you have your basic stock, lets say your initial stocking load generates 100,000 units of waste, and you start with 100 bacteria. So start 100, day two 200, day three 400, day four 800, day five 1600 and this continues until at some point part way through a day you will have exactly 100,000 bacteria. Finally after this point waste levels start declining, but tests will still show some. One day afterwards you now have 200,000 bacteria, and tested waste levels drop to zero shortly after this. But since 100,000 units of waste will support 400,000 bacteria the numbers still climb but more slowly since they don't have max intake.
What this means is your biofilter has the potential to have a surplus capacity over and above the current production levels of waste. Now in reality there are specific conditions that determine whether you have a large surplus capacity or hardly any at all. So it is wise to pay attention any time you add fish, but it is quite possible that your biofilter had enough surplus capacity to deal with the increase.
It is also possible to damage your bacteria colony that make your biofilter enough to destroy your surplus capacity and have readable ammonia or nitrite levels at any time, which is why we take some precautions with how we treat our filters, and don't recommend the usual cleaning style done to fish bowls which is to take everything out and scrub it down.