All of the numbers that we wrote is optional. The truth of the matter is to really receive the blessing of Hashem each one should give according to his ability.
This is exactly the idea of Maaser, that you give 10-20 % of your income on a regular basis for tzedakah.
It was said by many big and righteous rabbis throughout the generations that the best option for tzedaka is for poor people that are learning Torah in Yerushalayim specifically.
Your donation goes toward those poor people who are learning Torah here in King David’s tomb in the holy city of Yerushalayim.