ComBat returns negative expression value

Question

[Grace]

Hi, I am trying to use ComBat function to remove the batch effect:

combat_data <- ComBat(dat = trans_log, batch = colData$batch)

But it returns some negative value, I'm not sure if this is because the batch effect itself is not obvious?

Can I use the negative value to do WGCNA analysis, or I don't need to do ComBat? (Because my batch effect is really not obvious)