Set the maximum decimal precision that can be displayed in the report. Report viewers can set the precision to predefined values without requiring access to display settings. Users will not be able to increase the precision beyond the assigned value.
SETMAXDECIMALPRECISION(value)
value - Maximum number of digits that can be displayed after the decimal point
SETMAXDECIMALPRECISION(8)
//Sets the decimal precision to 8

Setting the maximum precision to 10 digits
Notice how the increase precision button gets disabled after the configured limit of 10 digits:

Setting maximum decimal precision with scripts