Is 1GB more than 250MB

Assuming the 1G refers 1 GB(or Gigabyte) no, 256mb is not more than that.

MB, or a Megabyte is equal to 1,000,000 bytes. Therefore, 256MB is 256,000,000 bytes.

Whereas a GB, or Gigabyte is equal to 1,000,000,000 bytes.