Okay, so the handedness of the map creator may not be a factor in the order of the numerals.
So; other factors to consider:
Base #: this may not be base 10. Considering the focus on 3's I'd think something based on 3s is just as likely: possibly either Base 3, Base 6, Base 9 or Base 12. The base will tell us the number of unique glyph symbols that are represented in a given counting system.
The meaning of glyphs/digits in representing numerals: in the arabic system we use, each glyph/digit represents one numeral in a base 10 system, with each additional glyph/digit to the right indicating a power of 10. Using the same system, but changing the base, as above, to let's say a base three system would give us three different glyphs: one for 0, for 1, and for 2. Each digit to the right (assuming the numbers are ordered from right to left in the arabic system) would represent an increased power of 3. Thus the glyphs 10 would represent 3, 11 would represent 4, and 12 would represent 5, 20 would represent 6 and so on. However, this isn't the only way for the glyphs to represent value. In the roman system, for instance, each "I" represents a value of 1. If the I is to the right of another glyph, it is added to the value of that glyph. If to the left, it is subtracted from the value of it. Each V represents a value of 5, each X a value of 10, and so on, and consecutive glyphs of the same value are added together before either being added to or subtracted from the next-order glyph. Alternatively, the order of the glyphs could be reversed, so that, going back to our example, 01 represents 3, 11 represents 4, 21 represents 5, and so on, so that the higher-order numeral is to the right instead of to the left. The fact that our higher-order numerals are to the left, IIRC, is an artifact of arabic being written from right to left.
So... the order of the digits could have a variety of meanings representing different operations that are performed on the glyphs to arrive at a given value. Addition, subtraction, and multiplication are the operations most likely to be suggested by the order of glyphs (in arabic, it is multiplication by 10s, 100s, and so on), although it might theoretically be possible for digit-order to indicate divisions as well.
Other considerations might include the possibility of hybrid forms where the counting systems appears to represent more than one base, or where glyphs represent something other than pure value (i.e. mathematical operators, etc.) or hybrids of different types of counting systems (like a hybrid roman/arabic system, perhaps?) And besides the examples I've given, I'm not familiar enough with the topic to come up with other alternative counting systems from which to draw clues and conclusions.