Your question is unclear. Fertilizers are usually mixtures.
Do you want to get a fertilizer containing 2 g KCl + CaCO3 or do you want to get 2 g fertilizer containing KCl together with unfiltered CaCO3? As for the first possible question, it is the simplest stoichiometric calculation that each textbook writes about - all you need to do is read the relevant chapter with understanding, and then do the calculations.
These two points of requirements make me understand as in the second part of the question (2g of mixture KCl + CaCO3). In the first case you will receive about 2.2 g of fertilizer containing exactly 2 g of KCl, and in the second case - 2 g of fertilizer (mixture) containing about 1.8 g of KCl.
Decide what you really need to calculate and make the appropriate calculations (numbers 2.2 and 1.8 are only estimated, but rather close to the result of your calculations)