DevFee - means that this share was found by thread that handles 5% developer fee. Target is the share value that is defined by pool (lower target - cheaper share), most pools adjust target to achieve some average speed of shares, too low target will cause a lot of cheap shares and pool overload, too high target will cause you can search for a share for a long time. Since developer fee is handled by separate thread and it has only 5% of total power, pool sets much less target for it, as result you will see "dev fee" shares more than 5% of total shares but these shares are cheaper than main shares (in your example 1941 and 20000 so dev fee shares are >10 times cheaper than main shares).