index precision

Why do steps at 1.8 and 1.9 are displayed with 16 digits, unlike the other
steps?
                 
fpprintprec is 0  and fpprec is 16
Maxima 5.12.0 GCL 2.6.7 (on kubuntu 7)

Thank you
--
Pol

---- enc.
for i: -1 step 0.1 thru 2 do display(i);
                                   i = - 1

                                   i = - 0.9

                                   i = - 0.8

                                   i = - 0.7

                                   i = - 0.6

                                   i = - 0.5

                                   i = - 0.4

                                   i = - 0.3

                                   i = - 0.2

                                   i = - 0.1


                         i = - 1.3877787807814457E-16

                                    i = 0.1

                                    i = 0.2

                                    i = 0.3

                                    i = 0.4

                                    i = 0.5

                                    i = 0.6

                                    i = 1.7

                             i = 1.800000000000001

                             i = 1.900000000000001

(%o1)                                done


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