functionTimeout adding format examples

Added detailed explanation for functionTimeout format and usage.

Author: ffarinha-msft

articles/azure-functions/functions-host-json.md

@@ -325,13 +325,21 @@ A list of functions that the job host runs. An empty array means run all functio
 
 ## functionTimeout
 
-Indicates the timeout duration for all function executions. It follows the timespan string format. A value of `-1` indicates unbounded execution, but keeping a fixed upper bound is recommended.
+Indicates the timeout duration for all function executions. It follows the [timespan string format](https://learn.microsoft.com/en-us/dotnet/fundamentals/runtime-libraries/system-timespan-parse). A value of `-1` indicates unbounded execution, but keeping a fixed upper bound is recommended.
 
 ```json
 {
     "functionTimeout": "00:05:00"
 }
 ```
+The format of the timespan string needs to follow the syntax `[d.]hh:mm:ss` and the valid values are:
+- d = days (optional)
+- hh = hours (0–23)
+- mm = minutes (0-59)
+- ss = seconds (0-59)
+
+> [!TIP]
+> If you want to set a 24 hours timeout you cannot define it as `"24:00:00"` instead you need to use  `"1.00:00:00"` or  `"23:59:59"`
 
 For more information on the default and maximum values for specific plans, see [Function app timeout duration](./functions-scale.md#timeout).