Items with serial numbers
Add New Item
Go to Inventory-Equipment Settings-Items logical categories
Image: Items logical categories
Click ADD NEW ITEM button
Enter new Item's data and check TRACK ITEM BY SIZESS/N OR ANY UNIQUE IDENTIFIER radio button
Enter Serial Numbers
Click SAVE button
Image: Add new Item
Select item from list to: Check Details, Edit Item, Enter Quantities...
Image: Select Item from list
Check Item Details
Image: Item Details
Edit Item and click SAVE button
Image: Edit Item
Enter Quantity for each size and click SAVE button
Image: Enter Quantities