lib2db---Waring 问题请教。

在DC里，用了read_libXX.lib
有很多warning如下:
Warning: Line 211468, Cell 'XOR3X4', pin 'Y', The 'values' attribute has a '-0.089602' value,
which is less than '0.000000' the minimum recommended value of this attribute. (LBDB-272)
Warning: Line 211468, Cell 'XOR3X4', pin 'Y', The 'values' attribute has a '-0.032635' value,
which is less than '0.000000' the minimum recommended value of this attribute. (LBDB-272)
Warning: Line 211574, Cell 'XOR3X4', pin 'Y', The 'values' attribute has a '-0.045365' value,
which is less than '0.000000' the minimum recommended value of this attribute. (LBDB-272)
Warning: Line 211656, Cell 'XOR3X4', pin 'Y', The 'values' attribute has a '-0.003312' value,

怎么会是负值啊?不应该的吧?是不是哪里错啦?
lib里面定义的肯定是正值啊。

这样还能output成.db 的格式还能用吗?
write_lib -format db XXX -output XXXX.db

可以有负值的

是吗?能介绍下，这负值是怎么转换出来的吗?
lib里定义的都是正值啊。
谢谢啦，，，