The explanation its simple.
You have 2 ways to tell which card you are holding.
First card the "easy" way which is just by lookin at the left border of your playing card and locating the "odd" split splade, problem with this one is that the cards 3 - 8, 4 - 9, 5 - 10 and 6 - J share a marking (each pair). So you end up in a 50/50 situation.
The hard way is through those markings, to read the marking system you need to use the "magic eye" (im not joking, the optical illusion used in this deck its called that way) check on google to see what kind of illusion and how to spot it.
This illusion makes this deck THE MARKED DECK, you need to know which lines are which but after a while (and mixing both ways to read the marking system) you end up just memorizing 4 different patterns.
As you can see on the image the " low values" ( 3, 4 ,5 and 6) run a line from your lower left corner to your upper right corner, if you spot lines running that way you will know what value your card has.
For the High value cards you need to spot diagonal lines running from your upper left corner to your lower right corner.
So taking everything into account to read the marking system i recommend.
1.- Spot your "odd" split spade.
If its an A, K, Q, 7 or a 2 you are safe, since this cards have unique markings and you can jump to step 3
Also 7s and Qs share the same Odd split spade but the 7s have an extra odd split spade, just above the heart suit mark.
2.- If the card its a 3,4,5,6,8,9,10 or a J look for the Diagonals.
Lower left to upper right means its a "low" value, Upper left to lower right means its a high value.
Extra tip:
For an easier time locating the diagonals, start at the "odd splitspade"
3.- Locate the suit marking
4.- Reveal
Hope that helps
