Quantification refers to the process of of analyzing a feat and determining what it means in terms of power. This is often done via calculations. Naturally, some feats are harder to quantify than others, whether it is because the calculations are complex, or there is missing/unknown information, or there is simply no way to quantify it. In the latter case, it is referred to as being unquantifiable.
Feats that are completely unquantifiable (like breaking dimensions in a continuity with no precedent for how much power that takes) are considered worthless if taken out of context. For example, if someone blasts a hole from one dimension to another, it could be inferred that said character can travel across dimensions and possibly escape dimensional BFR attempts, but it says nothing about their actual destructive capacity.
Feats that are completely unquantifiable (like breaking dimensions in a continuity with no precedent for how much power that takes) are considered worthless if taken out of context. For example, if someone blasts a hole from one dimension to another, it could be inferred that said character can travel across dimensions and possibly escape dimensional BFR attempts, but it says nothing about their actual destructive capacity.