I think that you mean "numerals", not math in general.
In our system (and in the Arabic "Indian" system, as pointed out by a fellow reply) numerals are written with the least significative figure to the right, so in that sense it's like com.twitter@holysee.
However, the author has acknowledged that there was a minor error in the post, so this is a case of a retrofitted explanation :-)
In fact, notations do not have to be consistent about digit significance. See, for example, US dates (9/11/2001) or German (and Arabic) long-form of most two digit numerals, which are read backwards, as in "four and twenty blackbirds" (happy to be corrected about Arabic...).
Even in Arabic, numbers are the exception, written from left to write.
انا من مواليد ١٩٨٦.
I was born in 1986.
You will notice the number sequencing, although slightly different looking, is the same as in Western orthography. Why? Arabs took their numbering system from the Indians, and adapted it.
The only way in which it makes sense to talk about numbers being written "right to left" or "left to right" is when comparing the order of speech sounds to the ordering of numerals read. In English it goes from the biggest to the smallest: "420" ==> "four hundred and twenty".
Then German and Danish are neither left-to-right nor right-to-left, since 123 is einhundertdreiundzwanzig or hundredetreogtyve ("onehundredthreeandtwenty"), so that doesn't seem to work too well, either...
Numeric notation is built right to left. To count up from 1 to 9 uses single digits, of course. Then to go from 9 to 10, the ones place increments and rolls over, and we add the new tens digit on the left, not the right.
What does it mean to be right-to-left? If it means that least significant values are on the right side and most significant ones on the left side, then domain names are left-to-right (as opposed to numeric notation).
com.twitter@holysee
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By the way, this must be a mistake:
This is a clearly a byproduct of the right-to-left language of the designers of these systems