According to this Solubility graph, we can conclude that at 70°C, we will have a value around 150 grams of KNO3 being able to dissolve in 100 grams of water, since these solubility graphs will usually work with the constant value of 100 grams of water. We can't have the exact value since the graph does not show the 70°C temperature exactly, but it is very close to this value 150 grams