Neat. Wonder why no one else thought of that.
The extended numbers are MAPxy where x is a letter, A-Z, and y is 0-9A-Z. Example: 98, 99, A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, AA, AB, AC, AD, AE, AF, AG, AH, AI, AJ, AK, AL, AM, AN, AO, AP, AQ, AR, AS, AT, AU, AV, AW, AX, AY, AZ, B0, B1...
Straight out hexadecimal was considered, but because it would introduce hidden levels between 09 and 10, we decided not to go that route. This way provides 1035 slots.