Hi @Anonymous,
Do you want to extract Antal value of each Vare and save them back to SharePoint list?
Please take the following configuration for a reference.
Add a trigger When a new event is created.
Add the action HTML to text to convert the body to text.
Add compose2 use the following code to get the starting position of Kidevand:
indexOf(body('Html_to_text'),'Kildevand:')
Add Compose3 to get the starting position of Antal value of each vare:
add(outputs('Compose_2'),10)
Add Compose4, get starting position of Sodavand:
indexOf(body('Html_to_text'),'Sodavand:')
Add Compose5, get Antal value of Kidevand:
substring(body('Html_to_text'),outputs('Compose_3'),sub(outputs('Compose_4'),outputs('Compose_3')))
Add Compose6 to return Antal value of Sodavand:
substring(body('Html_to_text'),add(outputs('Compose_4'),9),2)

Hope it could be your reference.
Best regards,
Mabel