PT 分析中的RC-009 Warning 的问题

jiangsuren

在用PT读入spef文件做timing sign-off时，发现有这样的warning
“the drive-resistance for the timing arc u_xx_sda/PAD--->C is much less than the network impedance to ground ;
PrimeTime has adjusted the drive-resistance to improve accuracy.(RC-009)"

请问，这样的Warning对于signoff有什么负面影响吗，为什么会产生这些Warning呢？