Negative absorbance has no physical meaning except the fact that the blank absorbs more light than your sample.

What does negative absorption coefficient mean?

A negative extinction coefficient essentially means that you have amplification or gain rather than absorption. If gain is unlikely with your sample then you must have some kind of error either in the measurement or calculation. ... It means nothing.

Can absorbance value be negative?

A "negative absorbance" means your reference is absorbing more than your sample. You have a "zero error".