Hi john when we get the basis to get the unexpired basis, what is the primary reason of deducting LIBOR from 100 when we are deducting whole interest rate( including the movement and the LIBOR) when we estimate the expected future price using the unexpired basis and the interest rate.
Because this is the way interest rate futures are quoted in real life. A price is needed in order to be able to buy and sell, and this is the way that it was decided to do it. How they are used is all explained in my free lectures.