The CPT bid will be calculated by the formula following the metric you specify as your target:
The rule also takes into account Upper and Lower bid limits you specified. In case the new bid is below the Lower bid limit you specified in the rule, the system will set the bid to the lowest limit. If the new bid is higher than the Upper bid limit, the bid will be set to the highest limit specified.
Target Metric: CPI
Target Value: $3
The rule will analyze the data looking back on the Date Range you specified before making any adjustments. Let's imagine the rule runs and finds a keyword has 180 taps and 70 installs for the outlined period. How the bid will be adjusted towards the target CPI?
The system will follow the following formula: Bid = (Installs / Taps) * Target value.
New CPT bid = 70 / 180 * 3 = $1.16
As $1.16 is in the range of [0.5; 2] (Lower and Upper bid limits), this bid will be set for the keyword.