Hi
It is in Operators and Functions in the manual
r_ticks(original_price, ticks)
Returns a price that is ticks higher or lower than original_price. If ticks is positive the returned price will be higher, and if it is negative the price will be lower.
For example: r_ticks(6, 4) will return 6.8, and r_ticks(4.1, -5) will return 3.8.
Note that for Asian Handicap markets a tick is equal to 0.01 regardless of the price range.
The expression r_ticks(original_price, 0) will return original_price adjusted for the correct value based on its price range. E.g. if you write r_ticks(10.17, 0), it will return 10.0, if you write r_ticks(2.57, 0), it will return 2.58 and so on.