A couple of data points that compare the measurements from the PC (v.1.2.1) and Android (v.4.0.1 , 12JUN2024) apps. All measurements were taken 50cm from the sensor.
Nichia B35AM 5000K R9080. Measured at 4/7 output. Both apps work well. R9 (87.5) in PC is slightly higher than Android (81.6)
LatticePower CSP2323. Measured at 4/7 output. Some differences in Ra and R9. R9 in PC (85.1) is much higher than Android (45.0). The R9 measurements are somewhat apart from koef3’s measurement of 67. I think the PC version is overestimating the R9 of CSP2323.
Osaram P8. Measured at 65 lumen output. PC version works well. Android app does not provide Ra nor R9. PC app correctly measures negative R9.
CCT and duv measurements are very similar between the two apps.