Hello again @Anonymous 😺.
The reason you are having trouble is a Text Input inside of a form will not accept Text(ThisItem.Time,"[$-en-US]00:00") if the SharePoint column is a number type. This is because the form wants to ensure only a number is accepted into the SharePoint list once submitted.
In your situation I would recommend a using dropdown instead of a Text Input anyways. It is better because you can restrict the user input to only times you assign. It does take a small bit of work but I will give directions below.
First, please take a look at the sample app screenshot. This is what we are working towards.
#1 Delete your Text Input within the Time_DataCard (some errors willl appear but don't worry about them yet)
#2 Add a dropdown control to the Time_DataCard with the following properties
Default: Text(ThisItem.Time,"[$-en-US]00:00")
Items: ["00:00","00:30","01:00","01:30","02:00","02:30","03:00","03:30","04:00","04:30","05:00","05:30","06:00","06:30","07:00","07:30","08:00","08:30","09:00","09:30","10:00","10:30","11:00","11:30","12:00","12:30","13:00","13:30","14:00","14:30","15:00","15:30","16:00","16:30","17:00","17:30","18:00","18:30","19:00","19:30","20:00","20:30","21:00",
"21:30","22:00","22:30","23:00","23:30"]
#3 Change the Update property of Time_DataCard to this code
Value(Substitute(Dropdown_Time.Selected.Value,":",""))
#4 Look at the App Checker for any errors caused by Step #1 replacing any references to the original Text Input or deleting the code entirely.
Hopefully you enjoy this approach. This is the full realization of what I had in mind during my original response. Let me know.
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