High hydraulic conductivity values while using PEST

[DT21CIV011 RAKESH K. VERMA]

Hello there, I am using MODFLOW6 in ModelMuse for groundwater analysis. I am using PEST auto calibration using pilot points. I have assigned  0.00001 to 100 lower and upper bounds, respectively, of hydraulic conductivities in different zones. Model runs good, but model estimated very high hydraulic conductivity values ranging from 4E-4 to 21000 meters per day. I am simulating a two-layered aquifer system, unconfined and confined in nature, with 15 piezometers. 

Can anybody suggest what I am missing? And are the hydraulic conductivities real for a weathered/fractured/jointed aquifer system?