I am trying to calculate the flow length for a number of Subbasins in the Mary's River Watershed in Oregon. I am doing this in order to calculate the time of concentration for each subbasin.

My problem is that the output raster from the flow length tool shows values that I cannot decipher. I don't think it's shown in terms of cell size either. The cell size for the map is 0.00027777778. The greatest flow length value in one of my subbasins is 0.143758. Dividing this by the cell size gives 517.5. I roughly measured the distance of the channel using the measure tool, and it's around 6,000 meters.

What sort of units is the flow length output giving me?

Any help would be greatly appreciated, for I've scoured the web and can't find anything to address this concern.

I've posted a screenshot below to give some sort of reference to my problem.

Your data probably don't make sense, since I suspect they are in decimal degrees (aka a Geographic Coordinate System, GCS) whereas, they should be in projected coordinates. The simplest thing would be to project the data prior to running any analysis that requires any geometri measures such as area and/or length. Depending upon the size of the study area, project to an appropriate projection like UTM, albers, lambert etc etc

PS whenever working with raster data, choose a cell size appropriately, if the cell size is too coarse, area/length estimates will be less similar than those one would obtain from vector analysis... a cell size too large, leads to processing and storage issues.