Hi,
The charge in your screenshot is for AVD Per User access pricing, which is for external users only. Under per user access pricing, you are billed (£8.124 for Desktop and Apps, or £4.468 for Apps only) for each unique user that connects during the month, regardless of how many hours. Based on what you have written in your description you had 3 users connect, which would amount to £24.37 fee under per user access pricing.
The above charge only covers licensing for external users. Cost of compute, storage, bandwidth, and other Azure resources you may be using are additional.
For testing (just yourself is what I'm assuming) I would recommend you get Microsoft 365 Business Premium and use that to cover your licensing instead of using per user access licensing. Again, per user access licensing is for external users, which likely means it isn't correct for your use case. You will need to opt-out of per user access licensing.
Article below explains some of AVD licensing:
Per-user access pricing for Azure Virtual Desktop
Below is the Azure Virtual Desktop pricing page. Please scroll down to the Virtual Desktops section and look on the right hand column for the list of licenses that give you eligibility to use Windows 10/11 with AVD. If you create a Windows Server host pool you would need to have RDS CAL or equivalent (also on the licensing page).
https://azure.microsoft.com/en-us/pricing/details/virtual-desktop/
If the above was useful please click Accept Answer.
Thanks.
-TP