Both, the Maya numeral system and our decimal numbers are positional or place-value notations, which is to say that the same symbols are used to express different orders of magnitude.
There are two major differences:
1. In the decimal system symbols are positioned from left to right in decreasing orders of magnitude, whereas Maya numbers are positioned top to bottom in decreasing orders of magnitude.
2. In the decimal system orders of magnitude progress in powers of ten (base 10), while Maya numbers progress in powers of 20 (vigesimal or base 20).
This app simultaneously displays user generated Maya numbers and their equivalent decimal values at each order of magnitude, as well as the final decimal equivalencies for Maya numbers 1 to 1,279,999,999.
Fixed two overlapping UI elements.
Ratings and Reviews
While the representations from 1 to 19 are correct, the symbol shown for twenty is actually their "zero." The conversions totally ignore the Mayans' use of place value. I would not recommend this to my students.
I'm puzzled at your comment that my app "Learn Maya Numbers" does not represent the number 20 or for that matter the numbers 1 to 1,279,999,999 correctly.
It appears to me that you don't know how to use the app. Please tap on the information button on the lower right corner of the screen to access instructions on the proper use of the app.
Once you have verified that the app is in fact working correctly, I think it would only be fair for you to retract your negative review.
Conversion of 20 works
I don't know if the other reviewer is referring to an older version, but I downloaded this app and it represented twenty as a shell in the zero column and a dot in the twenty column as I would expect. This app appears to me to work as advertised. You can convert from the decimal system to mayan or from mayan to decimal. Maximum representable number appears to be 1279999999.
With Family Sharing set up, up to six family members can use this app.