Hey there @Invexendo 👋
If SimplyBook is sending the amounts over as 15.00.00 and 120:00.00.00 then I’d recommend reaching out to our Support team to have that investigated in case it’s due to a bug.
In the meantime, I think you’d need to use two Formatter actions to get the amount converted correctly. I don’t think a Formatter (Numbers > Format Currency) action would be able to convert the amounts correctly since it would expect to be receiving a number in a currency format not a time format to begin with. So you’d need one Formatter (Text > Replace) action to replace the colons (:) in larger amounts with a period (.).
For example:

This would convert amounts like 120:00.00.00 into 120.00.00.00:

Then you’d have a second Formatter (Text > Extract Pattern) action to extract the the number up to two decimal places. Use ^\d+\.\d{2} in the Pattern field like so:

And that should output the value to two decimal places e.g. 120.00.00.00 becomes 120.00:

Then in your Google Sheets action you’ll select the value output by that second Formatter action.
Let us know how it goes! 🙂