The shares are identical, there are no numberplates on shares.
You pick whichever parcel suit your needs, either size wise or pricewise.
Once you own shares, you can sell 1, 100 or 1,000. (Don't short them) Just need to track brokerage for your accountant.
You can sell first in, first out, last in first out, whatever works for you to keep your head around. Just keep good records.
To keep my paperwork simple, up till now have been selling parcels in the same quantity I bought them in. Staple the buy/sell contract notes together and record that in my buy/sell spreadsheet.
