There is a limit of 250 tabs. I'm not sure if it's per day or not.
That's equivalents to:
10 Vaccinations
25 Books
1.3 Person's clean water
2.5 Square feet of shelter
25 Trees planted
That's equivalents to:
10 Vaccinations
25 Books
1.3 Person's clean water
2.5 Square feet of shelter
25 Trees planted