In my experience the first 3 digits tells you something about the potential of the person. Jan Scholten wrote that each following digit of the first 3 ones cannot be bigger than the previous one.
For example: 64x, there can be 641, 642, 643 and 644, … but no 645, because the last digit 5 cannot be bigger than the previous 4.
This is a restriction in the potential development of the character, maybe due an bigger defect in the DNA or a trauma during pregnancy.
A “ordinary man”, 664, last digit 4 points towards the ferrum series, can develop towards 665 silver series and acquire true artistic skills and preferences. Or 665 can develop towards 666 Lanthanides series, desire for independence and more personal development.
If you analyze the plants from 1xx to 4xx for example you will notice that many symptoms reveals genetic defects or autism.
642 can reach 644 in a few years, let’s assume in 2 years. Then 642 could reach 665 and become an artist in 23 years (just a guess). This means that someone with a genetic defect now is unable to reach this goal, because 442 needs 223 years, more than the actual life span of humans.