Deleted folder caused whole box drive to sync from scratch on laptop

Hi, 

I have deleted one folder from my box (15gb data) on my laptop today and this caused all the other folders/files to start to sync on my laptop. I don't get it.  First, I thought I forgot to upload  some files to certain folders, because they were missing, then I realised that they have been added and are in the box cloud accessible from other devices, but disappeared from my laptop. It seems like all the files are being synced again on my laptop. This is strange.  The process is still ongoing, at the moment it looks like I am losing my files from my laptop. In some folders there are less and less.  Can someone advise on this? Thank you.