Reference level and mix level SPL ????

[cminor]

One possible client is requesting this parameters and I am a little over my head ..
I have some amator mixing experience but... maybe I can't understand right the requests:

Reference level: –20 dBFS

Peak level: –10 dBFS

Dialogue level (dialnorm): –27 dBFS

Mix level: 105 dB SPL

the only thing I understand is peak level... (the maximum level on that track should be -10 dB)
but the rest is too much =))
Dialog level I presume is the Voice Over level middle not maximum...
But reference and Mix level ?

Can some one please explain me what they are?
How can I measure and what to measure for those requests?

Many thanks