Property transfer version 5.7.2 not removing double quotes.

I am doing property transfer by using the setup script through sql. My request has something which should be in []. I have created the propert transfer like below 

For the Target i have given like below.
$.dispositionIds


In the setup script I am giving like below.

String dispositionIds = rows.DISPOSTN_ID

//Set Property value
testRunner.testCase.setPropertyValue( "DISPOSTN_ID", dispositionIds )

After runng the script I am getting the value in double quotes "" like shown below.
"dispositionIds":"[1282678]" ---But becasue of the double quotes, My request is thrownig an error saying invalid json.

My Colleagesue have a differnt verison soap 5.6.0 and it is working fine for them.