Let me explain
TPM is ticketed point mileage which are the actual miles flown an a non-stop sector route from airport to airport in great circle distance.
MPM is the maximum mileage permitted in fare calculation.MPMs are published in the IATA mileage once a year. This means that the TPMs must not exceed the MPM for a fare to apply with no surcharge.
CUM is cumulative and it is the sum of all TPMs.
EMS is the excess mileage surcharge . This is the extra miles allowed in the MPM which can range from 5% to 25%. This means that if the TPMs are higher than the MPM you will have to increase 5 % to 25 depending on the range of the miles flwon.
DED is deduction published in the EMA excess mileage allowance in some routes some carriers need to compete with others but they don´t have direct flights so they IATA agrees to apply mileage deductions via certain points.
Example you want to fly from BUE to CCS but you need to have a stopover in SAO. If you check TPMS BUE SAO CCS this will excede the MPM,so granting 500 miles will let you apply a non increased through fare from BUE CCS.
LAST would appear when the TPMs exceed the MPM .
NEXT are the remainins TPMS you have deducting tpms from MPM.
25 is last amount of the last increase by 25% of the MPM. So this means that if you exceed that amount you would have to look for other options for fare construction.