Check the date and reduction
First, reject impossible dates instead of letting a programming language normalize them. 31 April is not 1 May. Leap-year handling also matters: 29 February exists in 2000 but not in 1900. Second, keep 22 unchanged. Third, do not reduce values below 23 merely because they have two digits.
These errors can change every later position. Test boundary dates and simple values such as 19, 22, 23, 28, and 44 before evaluating more complex charts.
Do not mix construction rules
Fourth, use one reduction convention consistently. Digit addition and subtraction of 22 produce different values. Fifth, reduce each completed personal node before using it in a subsequent formula.
Write the steps for 28 November 1987. The correct digit-sum anchors are 10, 11, 7, 10, and 11. This example exposes several reduction mistakes that an easier date can hide.
Pair complete compatibility nodes
Sixth, calculate both personal charts before adding corresponding compatibility positions. Rebuilding all inner points from combined anchors can produce a different chart.
The purpose section has its own documented sequence: pair the constituent sky, earth, paternal, and maternal values, then derive the paired purpose totals. Test this separately from ordinary node pairing.
Keep labels consistent
Seventh, do not silently import a different Tarot numbering scheme. This site uses Justice 8, Strength 11, and Fool 22. Also make sure a click on a visible chart point opens the interpretation for that exact point.
A numerically correct engine can still display the wrong reading if position identifiers are mismatched. Check the result cards, downloads, and interactive labels against the same computed object. Correct arithmetic needs correct presentation too.
A question to carry with you
What part of this reflection can I check against my own experience?
References & context
References for the calculation method and Arcana tradition.