The floating point representation need to incorporate three things:  Sign  Mantissa  Exponent
In the video lessons, 8-bit storage is used to demonstrate the working of floating point notation with the help of examples where 8-bit storage is divided as:
 1 bit for Sign.  3 bits for Exponent.  4 bits for Mantissa (the mantissa field needs to be in normalized form as discussed in the video lesson).
For the discussed 8-bit floating point storage:
A. Encode the (negative) decimal fraction -9/2 to binary using the 8-bit floating-point notation.