Hi Aaron,
Apologies for the confusion caused. I will get the documentation reviewed.
In actual, both of the documents are correct. If you uploaded 10 records with say 2 signals in first overwrite file.
Now, that you want to have additional 2 signals for only 5 of the records, so in this case, you will have to add 5 record rows with 4 signals (2 existing and 2 new). If you will add only 2 new signals, then the .overwrite file will unrealize (unrealize traits) these 5 IDs for old 2 signals.
For updating existing data, if you use .sync file, then that will not unrealize these 5 IDs for old existing signals, even if you add only 2 new signals.
When I use signals, that means "key"="value" pairs.