In Flowers for Algernon, at the end of Progress Report 9, Charlie's IQ is 100. In IQ testing (i.e., Stanford-Binet Rating Scale, Lewis Terman, Wechsler IQ Test Ratings Scale), 100 is considered "normal." In other words, a person with an IQ of 100 is able to function normally but not able to do or learn anything exceptional. Charlie started out with an IQ of 68, so a jump to 100 is a great attainment.
During the time period of Progress Report 10, Charlie's IQ has skyrocketed so that he is now able to mechanically improve the dough mixing machine at the pastry shop so as to boost its productivity. This is far above the "normal" represented by 100 and also well below the IQ level representative of exceptional accomplishment.
Altering a machine with no prior education in the laws of physics and machinery is certainly beyond an exceptional accomplishment. On IQ tests, the sort of exceptional intelligence that can do basically impossible things on native intelligence alone, with no help from education or training, is well above 140, which is the threshold of "genius" qualifications.
Kids-IQ-Tests.com has very good descriptions of IQ levels.