HP 50g Graphing Calculator - Manual (Page 549)

Page 16-72
The following screen shots show the RPN stack before and after application of
function RSBERR:
These results indicate that Δy = 4.1514… and error = 2.762..., for Dx = 0.1.
Check that, if Dx is reduced to 0.01, Δy = -0.00307… and error = 0.000547.
Note: As you execute the commands in the DIFF menu values of x and y will
be produced and stored as variables in your calculator. The results provided
by the functions in this section will depend on the current values of x and y.
Therefore, some of the results illustrated above may differ from what you get in
your calculator.