Subtract ounces sold from total beginning to get remaining

Hello every one,
I am not a master in excel but i have seen lot of professional here, so i am looking for a small help.

I am making bar inventory sheet, in which I am calculating 1 bottle is = 750 ml ie 25 ounce from 1 bottle.
I have filled in the details in which I am considering 1 bottle = 0.25 Serving.
So if I exceed above 0.25 it should automatically calculate 1.00.
For Eg I have taken 1 bottle in stock ie 1.00 but when I close my shift and I sold 0.05 ounce.
So my answer in balance column should show 0.20 but its showing 0.95 which i dont want
If I sell 0.15 ounce the balance figure should show 0.10 but its showing 0.85

I am stuck and dont know which formula will give me the exact figure which i want,

I have atached excel file.
Looking forward for you kind help .
Regards

It would be great if someone just have a look on my attached excel sheet and i think its just a simple formula which i am not able to figure it out.
Really looking forward to it.

Regards