Why A repeater listens on one frequency (its input) and retransmits on another (its output); the difference is the offset, and your radio shifts its transmit frequency by that amount. On the 70-centimeter band (420-450 MHz) the standard offset used across the US is 5 MHz, either above or below the output frequency depending on the band plan in your area. The 70 cm band is wide enough (30 MHz) to support such a large split.
Watch out The 600 kHz figure is the standard offset on the 2-meter band, not 70 centimeters; 2 meters is only 4 MHz wide, so a 5 MHz split would not fit.
2 meters: 600 kHz. 70 cm: 5 MHz. Bigger band, bigger offset.