In PWC, "Cellar" refers to your entire wine collection that is managed by your account. However, many of our users have multiple physical cellars (home, wine storage facility, office, etc.) and need to be able to keep track of them all.
Most users will set the location field (Inventory tab) to include all locations of the wine. So if you have 2 bottles of a given wine record in WC1 (Wine Cellar 1) and 3 in WC3, it might say WC1, WC3 or more detailed with quantities - WC1 (2), WC3 (3). You are free to enter whatever you'd like in the location field, but codes like the above are generally good because you can search/filter on them.
When you subtract a bottle you would just update the location field appropriately.
So if you removed 1 bottle from WC3, you'd update the location field so it would change to: WC1 (2), WC3 (2)
Also note - if you have multiple cellars, you could alternatively create a custom field in Settings named Cellar or similar and use that to manage the physical cellar location. The location field would then only need to contain the location in that specified cellar (so maybe a rack location coordinate like C2).
Currently any custom fields would be displayed in the Main tab for every record but we do plan on allowing you to specify where you'd like your custom fields in the near future.
Another option that some of our users do is to keep their cellars completely separate so they'll create an account for each cellar. That would allow all of your reports to be specific to each cellar and they'd be managed in distinct databases. If you'd like to keep your wines at a storage facility completely separate from your home, this would be a good option for you.