One glucose molecule produces 4 ATP, 2 NADH, and 2 pyruvate molecules during glycolysis. Although 4 ATP molecules are produces in the second half, the net gain of glycosis is only 2 ATP because 2 ATP molecules are used in the first half of glycolysis. If the cell cannot catabolize the pyruvate molecules further via the citric acid cycle, it will harvest only 2 ATP molecules from one molecule of glucose.
Glycolysis is the sole source of ATP. If glycolysis is disrupted, the RBC fail their ability to control their Na-K pumps that need ATP to function, and eventually, they die. If the second half of glycolysis slows or stops in the absence of NAD+ or when NAD+ is unavailable, RBC will not produce a sufficient number of ATP in order to survive.
The number of ATP has been estimated between 35 to 30. The total number of ATP is not known exactly due to variance in the degree of coupling between the flow of protons through the ATPase and electron transport ATP which is the energy currency of the cell.