MSP430FR6047: USS design center ADC capture doesn't work when "Gap between pulse start and ADC capture" is set to value lower than 30us

Hi,

I am using EVM430-6047 

according to document slau720b.pdf, this parameter range is 3 to 9000, but when i set it to value lower than 30 like 25, the ADC capture function will not work. If I change this parameter to 30 and keep the rest unchanged, ADC will update. I need to set it to value between 10 to 30, how do i do that?

CYH