Why we take the log of the target variable has to do with the fact that we are interested in relative changes vs absolute changes of the target value. You can find more info here
As far as overfitting goes… The values look okay. The middle one should be the results on the train set vs the last one on the validation set. Yeah, if there is dropout used than it could account for the difference. But it could just as well be that maybe the period in the val set is just easy to predict? Unless I am not seeing something these numbers look quite okay.
It’s also hard to talk about overfitting to the val set as we didn’t mess around with the parameters too much and our model never trains on the examples it contains.