فَإِنْ كَانَ يَعْرِضُ لَهُ كَثِيرًا: بَنَى عَلَى غَالِبِ ظَنِّهِ،
Translation: If such doubt happens repeatedly, one acts upon the stronger judgment.
Predominant judgment means one of two possibilities is more convincingly likely. For example, if the person repeatedly doubts between three and four rakahs but genuinely finds four more likely, that stronger conclusion guides the count.
A random guess does not amount to predominant judgment.