Still in the preparation process ...

A bit offtopic, but still related:
I tried to repartition my N9 64GB. Decrementing p3 (MyDocs) to 37 GB, reserving 16GB for other OSes (partitions).
Had to use --force, as disk was mounted (done on dvice), so far so ...
Everything went well, sfdisk shows correct partitions. BUT the MyDocs is still presented to be 53 GB, both when using df or even in mass storage mode on Win.
Any ideas what I have done wrong? Or missed?
Just want to be sure this to fix before continue.

--edit
reason I ask here is juiceme told already in other thread that he repartitioned (used 4th for nemo) and I did not find related answer in TMO

Of course did a reboot.
And tried again with unmounted MyDocs, to no avail.