The person used Frit 3134 instead of 3124, it makes up 70% of the recipe. The glaze melted much more and ran off the ware. That sounds like an impossible-to-fix problem. But the motivation was the large quantity that had been made. It just so happens that these frits have very similar chemistry except for one thing: 3134 has almost no Al2O3. That means that kaolin can be added to the bad batch to source the missing Al2O3 (and replenish the shortage of SiO2 at the same time). Extra silica is also needed to restore the full SiO2. The new chemistry is not an exact match, the B2O3 is a little higher, but this should not be an issue. Of course a raw:calcine mix of kaolin is needed (to prevent the glaze from shrinking too much on drying and therefore cracking). From this calculation we can see that for every 100 grams of the original powder we need to add 10 EPK, 15 calcined kaolin and 17 silica. Of course, one would need to know the water content of the slurry, that is calculated as (weight wet - dry weight)/wet weight * 100. If the slurry was 50% water, for example, then every 200 grams of slurry would contain 100 grams of powder.
Glaze chemistry is the study of how the oxide chemistry of glazes relates to the way they fire. It accounts for color, surface, hardness, texturem, melting temperature, thermal expansion, etc.