In the Arduino library versions through 0013, the only way to read and write the built-in EEPROM memory was through functions that only support one byte of data at a time. When saving a number from 0-255, this is sufficient. When saving a larger number, you have to call the EEPROM routines more than once, to save a "high byte" and a "low byte" for 16-bit numbers, or even more often for bigger numbers or other data types that cannot fit in one byte.