-1.4 to 1.4, no ndigit

-1.49 to 1.49, no ndigit

-0.064 to -0.025, ndigit=2

0.025 to 0.064, ndigit=2

-0.0064 to -0.0025, ndigit=3

0.0025 to 0.0064, ndigit=3

-649 to -250, ndigit=-2

250 to 649, ndigit=-2