The DRC setting for spacing is located in the User Preferences. Go to View User's Preferences Routing and Spacing Rules. The Global minimum spacing sets the DRC spacing for all layers. Below in the Per layer minimum spacing you can set a specific value for individual layers. After entering the desired spacing value select Apply then OK to save your changes. You have just set the spacing the DRC will look for when reviewing your design. If you select 1 oz Cu this setting should be changed to no less than .006" for a PCB123 1 oz Cu order or no less than .013" for a 2.5 oz Cu order. You can also control the spacing value by modifying the properties of a ratsnest line or trace. The following post explains how to adjust the spacing of a net.
How to change spacing for a net or filled polygon
The larger spacing value is what will be reported if the User Preferences setting is different than the net setting.