what are the different parameters based on which @unique in Lotus Notes returns a unique value.
The documentation is incorrect when it says that @Unique() returns a "random, unique text value". It is not random, and in fact there is no random component of the value. It is not guaranteed to be unique.
The return value of @Unique is based on the username and the date/time. The first four characters are: First letter of first name + First letter of last name + Second letter of last name + Last letter of last name. The final six characters are a date/time stamp with a resolution of 1 second. I do not know how the encoding for that works. This value will always increase with time.