My apologies for not coming up with a reasonable documentation yet.
First of all: please don't use IDs that start with numbers, that will result in invalid formulas. Valid IDs would be "value_1st", "first" or "value1".
Now, about the IF function. You can expect Jazzy Form's functions to behave at least similar to those in popular spreadsheets programs. I.e.: IF(condition, value_if_condition_met, value_otherwise)
I'm not sure whether it were 2 separate examples or they belong together. Here is the joint expression, as two nested IFs:
IF(value1>10, value1*value2, IF(radio=1, value3*value4, 0))
In words: If value1 is greater than 10 then result is value1*value2, otherwise if the radio button is set to yes then the result is value3*value4, otherwise it's zero.
I hope this makes it a bit clearer.