synthesis的log裡總是有warning:Operating condition WCCOM set on design ...

Warning: Operating condition WCCOM set on design cnu_5_small has different process,
voltage and temperatures parameters than the parameters at which target library
fsd0a_a_generic_core_bc is characterized. Delays may be inaccurate as a result. (OPT-998)
這個warning是什麼意思?
設置如下
set target_library "fsd0a_a_generic_core_bc.db fsd0a_a_generic_core_wc.db"
set_operating_conditions -min_library fsd0a_a_generic_core_bc -min BCCOM  -max_library fsd0a_a_generic_core_wc -max WCCOM

set target_library "fsd0a_a_generic_core_wc.db"
不需要指定两个corner 的，指定最差的即可