We need more informations.
Which version of Lightroom do you use?
How many pictures do you have in your catalog?
From which version was your older catalog?
My catalog (approx. 80K pictures) was after the update to Lightroom Classic CC only half the size of the old catalog (LR CC 2015.12)
So it could be possible.
But on the first view the size of 388 GB seems to be a little unrealistic to me.
I'm with the Photography Plan of Adobe for a couple of years . Always the latest version. I have 101,000 pictures with LR Classic.