sending OData post to insert data returns already exist

Hi all.

I am trying to insert a simple row in Account Schedule. Schedule Name is already created in Account Schedules page. Issue is when i use postman to send data to account Schedule., I get following error

    "error": {
        "code": "Internal_EntityWithSameKeyExists",
        "message": "The record in table Acc. Schedule Line already exists. Identification fields and values: Schedule Name='',Line No.='10001'  CorrelationId:  eb85b786-d673-47d1-b43b-71b518998691."

My request body looks like this:

	"Schedule_Name": "IC1",   /// It is already in Account Schedules
	"Line_No": 10001,
    "Row_No": "10",
    "Description": "Total Revenue",
    "Totaling_Type": "Posting Accounts",
    "Totaling": "40100..40400",
    "Row_Type": "Balance at Date",
    "Amount_Type": "Net Amount",
    "Show_Opposite_Sign": false,
    "Dimension_1_Totaling": "",
    "Dimension_2_Totaling": "",
    "Dimension_3_Totaling": "",
    "Dimension_4_Totaling": "",
    "Show": "Yes",
    "Bold": false,
    "Italic": false,
    "Underline": false,
    "Double_Underline": false,
    "New_Page": false

Is it because of composite keys or Schedule Name is coming from related Table?

Please point me in right direction to resolve this issue.