AD5933EVAL, can't detect a correct phase angle


i recently bought an eval board and initially test it and i used 333ohms for rcal and 220 ohms for rfb, after the calibration, i used a z unknown which is a 330uf, the impedance was correct but the phase angles was always negative 20 to 0 phase value.  i sweeping from 5000hz to 100khz and i used the internal oscillator. my question is, what is the problem of my calibration test? 

thank you very much

added picture
[edited by: Renzlexter at 5:07 PM (GMT 0) on 13 Aug 2019]