Hey there, hvjordaan.
Let me provide some information regarding recording a quantity using the QuickBooks Online Essentials.
The ability to record a quantity when entering a bill is currently unavailable in QuickBooks Online Essentials. Please know that this feature is only available in QuickBooks Online Plus.
You can visit this article to see the list of features that QuickBooks Online Essentials have: https://quickbooks.intuit.com/za/pricing/.
For more information, go through this article: Set up and track your inventory in QuickBooks Online. This link also provides you the steps on how to add your products as well as tracking them.
Know that you can always visit our Help Articles page for QuickBooks Online in case you need some reference for your future tasks.
Please know that I'm just a post away should you need anything else. Wishing you a wonderful week ahead.