Not enough space to install mac OS Big Sur

Hi I having trouble to install Big Sur on my MacBook Pro 250GB, the actualisation is already downloaded, and I have 23GB of free space but the Install APP is asking 3GB more.

I have an iCloud with 2TB with 1TB still free, my Bin is empty, I d'ont have much apps, except Microsoft office, Skipe and Crhome, that's all. All my filles are in iCloud Drive or Photos (That is all ready seamless working with iCloud), I want every file there, there's nothing unwanted. My Desktop is empty.

Why is not iCloud Drive freeing more space on my Mac for me to install Big Sur, doesn't it should work seamless?

My flash storage says:

iCloud : 99.89GB

Apps : 22.8GB

Mail : 4.8GB

Music Creation : 2.39GB

System : 11.33

Others : 75.64

Available : 33.34