What exactly are you trying to accomplish? If this is a repeater and you're trying to program the talkaround frequency, you don't need to modify the Direct Frequency field, as the radio defaults to the output for talkaround once you select the Direct/Talkaround option per-frequency.
If for some reason you have a need to program an entirely different frequency other than the repeater output as the talkaround, then you need to enable the Direct Frequency Enable option in Conventional Wide. Be very careful in doing this, however, because that option affects every conventional frequency radio-wide. If you enable that option, you will have to then go into every conventional personality to manually enter the talkaround frequency parameters for every channel you have Direct/Talkaround enabled.
tl;dr Ignore the Direct Frequency field unless you have a very unique reason to make a talkaround different from the Rx/TS Frequency.