We use the following methodology to calculate Day P&L and Unrealized P&L in your Portfolio:

Day P&L Calculation:

• If the stock was bought today →
  Day P&L = (Stock LTP - Avg Buy Price)
  
  

• If the stock was bought before today →
  Day P&L = (Stock LTP - Stock Previous Close) 

Unrealized P&L Calculation:

Unrealized P&L = (Stock LTP - Avg Buy Price)

Since Unrealized Gain and Day P&L use the same formula when a stock is bought today, both values will be identical.