The withdrawable balance is the amount you can take out from your Tradejini account. It may vary from the ledger balance displayed because funds from equity and F&O trades aren't settled instantly. The exchanges typically take T+1 day to settle funds from selling equities and F&O trades to your Tradejini account before you can withdraw them. For example,  if you sell any share the credit for the same will be shown in the ledger, however it's withdrawal  is possible only after the receipt of exchange settlement which happens on T+1.