How BankNIFTY contracts work?

If you go here - https://www.nseindia.com/live_market/dynaContent/live_watch/bn_home_page.htm

you can see this image

Do you know what this means?
Although the lot size of BankNIFTY is written as 20, the “Define Weights for 1
Contract of Bank Nifty” is written as 25.
Then how to calculate?

download%20(9)

If you download that you will get a csv, for me, it is written -

Symbol,Units Required
BANKNIFTY,40
AXISBANK,152.0268
BANKBARODA,84.2131
FEDERALBNK,174.3426
HDFCBANK,181.1857
ICICIBANK,568.2401
IDFCBANK,117.3774
INDUSINDBK,45.1125
KOTAKBANK,117.9415
PNB,92.7577
RBLBANK,30.7892
SBIN,328.2083
YESBANK,162.9088

Tell me how it works?
You will see in the image here, No matter whatever, you “Enter Contracts for Nifty Bank” the value of “IDFCFIRST”, “RBLBANK” and “FEDERALBNK” will come 0.