A higher numerical gear translates to lower gearing.

With the stock 4.636 gearing, the driveshaft turns 4.636 times for each roatation of the axle.

Changing the gearing to 5.143 would lower the gear ratio. The axle would have to turn 5.143 times to rotate the axle once.

Bigger tires need lower gearing to turn them at the same RPM to achieve the same speed.