What are the Tapaas calculation formulas for GLV, PnL?

Below are the formulas Tapaas uses to calculate PnL and GLV:

DayPnl = Realised + Unrealised – Unrealised yesterday 
(the concept of daypnl only applies to A & B books)

GLV in USD = Realised + Unrealised (in A & B books) + Realised in T book 
(T book holds the balance)


Example application:
Let’s say we want to calculate GLVToday – GLVYesterday. If we use the “GLV in USD” formula from above we get the following:

GLVToday – GLVYesterday = (Realised Today + Unrealised Today)  (Realised Yesterday + Unrealised Yesterday [on A & B books] ) + (Realised Today T Book – Realised Yesterday T Book)


With the DayPnl formula, we can see that:

Realised Today + Unrealised Today – Unrealised Yesterday will be equal to DayPnl Today.

Thus, we can take out the 3 values (realised today + unrealised today – unrealised yesterday) above and substitute with DayPnL Today instead and the formula becomes:

GLVToday – GLVYesterday = Daypnl Today – Realised Yesterday + (Realised Today T Book – Realised Yesterday T book)

So, when you are expecting  “GLVToday – GLVYesterday = Daypnl Today“,
 
we can see that the difference we get is actually the rest of the formula, which is: i.e. – Realised Yesterday + (Realised Today T book – Realised Yesterday T book)