4. (7 points) When copying a problem, Lin Lin mistakenly wrote a repeating decimal as 0.123456. If the digits are correct but the dots indicating the repeating section were omitted, there are $\qquad$ possible original decimals.
【Answer】Solution: According to the analysis, 
if there is only one point in the repeating section, then it can only be above the digit "6";
if there are 2 points in the repeating section, then one of them must be above the digit "6"; the other may be above " $1, 2, 3, 4, 5$ ",
so there are $1+5=6$ possibilities in total.
Answer: The original decimal has 6 possible forms.
Therefore, the answer is: 6.