a question in building a counter

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transgalactic

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build a sinchronic counter modulu 4 that counts up and down
the counter has a control input X that desides if it counts up or down

i cant understand the part of x=1 in the situation table
it should count down then it should be D>C>B>A
i dont know why they have written the x=1 part the way they did it

https://img503.imageshack.us/my.php?image=img86821gz9.jpg

plus i can understand the next step of using the exitation table
i cant see what two numbers they take each time
for the exitation table

how they build it??
https://img394.imageshack.us/my.php?image=img86831wa5.jpg
 

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