Need to change the cost budget of a task

Hello,

We have created a cost budget and against a task, we have entered quantity=1 and amount=250000 and got it approved. 

Going forward there was an amendment in the budget against the task, now when we change the quantity to 740000, the budgeted amount becomes 185000000 and we are stuck at this point and not able to figure out how the amount is multiplied with 2500000.

After changing the quantity to 7400000 then The Burdened Cost Columns becomes 1849999750000 and the Average Burdened Rate has become 250000 and the Variance % (Current Budget) =100.

Please suggest