Oracle® Database Reference 10g Release 1 (10.1) Part Number B10755-01
Oracle® Database Reference 10g Release 2 (10.2) Part Number B14237-01
Bigfile Tablespaces Number of blocks 2^32 (4 GB) blocks
Smallfile (traditional) Tablespaces Number of blocks 2^22 (4 MB) blocks
2^32 blocks is 4294967296 blocks, but not 4GB! 4G could be understood as 4 billions, ok, but 4GB means 4gigabytes, and that tablespace could well be 128 TB.
So I suggest you replace 4GB with 4G and 4MB with 4M.