Your monitor is reading salinity, while your hydrometer is reading specific gravity. look at this table to convert from one to another.
http://www.drydenaqua.com/Graphs_tab...ficgravity.htm

your salinity should be aroung 34-35 which translates to 1.025 @ 76 deg F. One of your instruments is off. Try recalibrating the monitor because it seems too high.