Digits clearly untrustworthy due to floating point rounding error are visible by default in the result of an expression.

Reproduction steps:
  1) Open a new spreadsheet
  2) Enter "=7*0.1" in a cell, press enter
  3) Observe that the result is 0.7000000000000001

This result is of course an unavoidable consequence of using floating point arithmetic. However, arguably the very last digits of a result should not be shown to the user by default. Not only are these digits not accurate, but the user almost certainly doesn't care about the 14th decimal place of their result.

Showing three or four digits is a more appropriate default as this this likely to be the sort of precision that the user desires and should harmlessly conceal unreliable digits in most cases.