Issue: 

Want to create calcualted item which would sum the item value of 1 day.
But when i want to test the item i get error: 

Cannot evaluate expression: function argument "vfs.file.contents[/home/ubuntu/scripts/logs/test.log]" is not a numeric value at "sum("vfs.file.contents[/home/ubuntu/scripts/logs/test.log]",1d)" 

How to reproduce:
Create item with this key : 

test.log contains just digit 3

then create calculated item:

click on Test and then Get value and test

Either its a bug or sytax has changed? I understand that there is no docs for zabbix 7 calcualted items yet.

I tested exactlly the same on zabbix 5 and was succesfull to acomplish what i wanted.