Most conditions implemented in the Rules section of the Rulesheet use a single value in a cell, as shown: 

Figure 1. Rulesheet with one value selected in condition cell

Sometimes, however, it is useful to combine more than one value in the same cell. You do this by holding CTRL while clicking multiple values from the Condition cell's drop-down list. Then, pressing ENTER encloses the resulting set in braces {..} in the cell as shown in the sequence of the next two figures. Additional values may also be typed into Cells. 

Figure 2. Rulesheet with two values selected in condition cell
Figure 3. Rulesheet with value set in condition cell
The rule implemented in Column 1 of the preceding figure is logically equivalent to the Rulesheet shown in the following figure:
Figure 4. Rulesheet with two rules instead of a value set
Both are implementations of the following rule statement:

If you write rules using the logical OR operator in separate columns, performing a Compression reduces the Rulesheet to the fewest number of columns possible by creating value sets in cells wherever possible. Fewer columns results in faster Rulesheet execution, even when those columns contain value sets. Compressing the Rulesheet in Rulesheet with two rules instead of a value set results in the Rulesheet in Rulesheet with value set in condition cell.

Condition cell value sets can also be negated using the NOT operator. To negate a value, type not in front of the leading brace {, as shown in Negating a Value Set in a Condition Cell. This is an implementation of the following rule statement:

Given the condition cell's value set, the rule statement is equivalent to:

Figure 5. Negating a value set in a condition cell

Value sets can also be created in the Overrides Cells at the bottom of each column. This allows one rule to override multiple rules in the same Rulesheet.