Retime the Reveal Source

First off, I need to get control of the reveal source's timing. Since I'm going to need the original plate as well as the retimed version I'll duplicate the original FileIn and connect a TimeX to the copy, naming it "sourcetime". I chose not to connect the TimeX to the original FileIn because sending a node's output to differently timed branches can generate unpredictable results in Shake. By default, TimeX's newTime parameter follows the global time. I'd rather choose the new time as an offset from the current one, so I'll create a local variable, called offset, for this. I'll make it a float type variable just to be consistent with Shake's global time, even though I'm not working on fields for this shot so it's not strictly necessary. Now I can set the newTime parameter to "time - offset" and use the offset parameter to easily specify any number of  frames backwards or forwards necessary to get a section of image suitable for painting through over the wire.