Prostredný znak tejto postupnosti má hodnotu 3, t.j. mod(x) = 3.

Translations from Slovak:

1) The middle character of this sequence is 3, i.e., Mod (x) = 3.

2) The Middle character of this sequence has a value of 3, i.e. mod (x) = 3.

I do not understand this question,  would anyone else like to venture a guess?

I guess it's Mode of X = 3?