Key Results values do not accept decimals when entered as part of the Actual Value or Target Value in the Details flyout, but they are accepted in the Key Results grid (these attributes have a configuration of 2 decimals in Studio).
Steps to Reproduce:
Log in with a user with the English (United States) locale.
Create or open an existing Objective.
Navigate to the Key Results.
Create or open an existing Key Result.
Open the Details flyout and Navigate to Actual Value (or Target Value).
Use the Quick Create '+' button with the date of today, and for the Value column, try to enter:
Actual Results: '10.5' [dot '.' is decimal separator in English (United States) locale]: 'Use 0 decimals or less' message shown.