The Materials section on page 94 calls for between 2 and 4 10-kilohm resistors. In fact, you only need one resistor. On page 100, the schematic calls for a 1K resistor. You may need a higher value depending on the resistance range of your force sensing resistors and the weight of your cat. IF a 1K resistor doesn’t give you good values, try a 4.7K or a 10K resistor.