Why is an empty feature service over 2GB in size?

[LindsayRaabe_FPCWA]

I have a feature service in ArcOnline. It's basic enough: it's basic polygon type data with only 3 attributes and no attachements and single symbol symology. The data is a dissolved version of a different feature service to use as a bookmark layer (i.e. search and zoom to a whole plantation instead of a single section of the plantation). The difference is though that the plantation data in it's original form is 176MB in size, whereas the dissolved Bookmark layer is 2261MB. Even after deleting all the features from the layer, it still registers as 2167MB. 

Why is it so? 

I export the data to a FGDB, download it and check the size on my PC  and it's only 7MB?!?!?

This has become a problem (not one we noticed before) because it's consuming a lot of credits.  

[LindsayRaabe_FPCWA]

We've since discovered 2 other layers are doing the same thing, though one of them is even worse with a 7.1GB file size despite being an EMPTY simple point feature service. The other is 2.1GB though it does contain 5,464,106 points. 

[HuubZwart · Accepted solution]

Might be shooting blanks here, by any chance, do you have sync enabled and have (several) replica's registered on the service?

[LindsayRaabe_FPCWA]

There's a good chance that there are some offline copies (replica's?) of one of the datasets, though I still don't understand how it's such a large file when the other dataset I mentioned that it is based on is only 176MB and would also have just as many offline versions. 

[LindsayRaabe_FPCWA]

@HuubZwart turns out it was the replicas. I disabled editing on one of the layers (in preparation of republishing it) and the size dropped to 21MB. There were over 133 copies of the data in offline mode. Didn't bother republishing it - just reenabled Sync. Thanks for the tip.