S&S ISA tranfer to IE as cash allowance/limits

I have my ISA in Vanguard and I’m looking into transferring to IE. IE doesn’t provide all funds that I have in Vanguard (which I’m fine with) and the docs say these will be transferred as cash. I’m a bit confused by the word “cash”:

Will I be able to invest all of this cash or does this cash transfer contribute to the annual ISA allowance?

you can invest ALL of the transfered cash into investengine plus your new 20k allowance.