There are many ideas of God. The idea that the individual souls are the parts and parcels of THAT entity is according to me the correct one.
What does the individual soul being a 'part' mean? It refers to the difference in size i.e. quantity. A drop of ocean is a few milli-litres in volume as compared to the ocean.
What the 'parcel' means is this...the inherent nature of the individual soul is divine i.e. the sameness in quality. A drop of ocean is saline just like the ocean.
There is an important idea that needs to be mentioned which results as an outcome of the above two...which is the idea of 'Love'...'Love' is not possible if the parts thought that they were all different from each other. 'Love' is possible only because Part A shares the essence with God Who in-turn shares the essence with Part B.