When looking at the field, the seat numbers go from right to left. The lowest seat number in the row will be next the adjacent section with the lowest number. For example, Seat 1 in Section 128 is closest to Section 127 while the highest seat number in Section 128 is closest to Section 129.
Something to watch out for in Levis Stadium, however, is that not all rows have a Seat 1. There are many instances in this stadium where the lowest numbered seat in the row is greater than 1. For example, the seat numbers in Section 132 Row 1 range from 18-31, so in this case Seat 18 is on the right side of the section when looking at the field and it is closest to Section 131.