Hi,
You may have to enter the value for /650 (in your case it is 8M9T) in IT15 for the corresponding years. /650 is Add Tax payable & Surcharge which will form the delta tax.
How you are calculating in your online tool/manually ? I hope you use additional data for doing this. Same way what was the differential tax also is required in SAP for calculating sec.89 relief.
regards,
Bala.