The smallest number that can be made using each card once is 1356. The cards can be arranged in ascending order, treating the "dot" card as a decimal point placed to form the smallest value.

If the dot isn't meant to represent a decimal, then the smallest arrangement of the digits 6, 1, 3, and 5 would be 1356.

Would you like a breakdown of the reasoning or more examples of number arrangement?

Here are 5 questions related to this problem:

1. What if the decimal point is movable—how would the number change?
2. How does the smallest arrangement differ if the dot has a special meaning?
3. Can this puzzle be extended to create the largest number?
4. How many unique numbers can be formed with these digits?
5. How does the concept of "place value" affect this arrangement?

Tip: When arranging numbers, always consider both absolute values and potential placement of special symbols like dots for decimals.