D/A converter with 0.4 up to 4V voltage output
You have made a digital-to-analog converter using an R2R ladder. Whether you like it or not, the voltage range for the output is determined by the full range of binary inputs, 0 to 15 rather than 0 to 9. The value of the LSB is 4V/16 = 0.25V rather than 4V/10 and the output voltage for a digital input of 9 (decimal) will be 2.25V.

To get the results you expected you need to increase the supply voltage from 4V to 6.4V, except that you can't get any voltage out with all of the switches open.