This is to add structure for Jumping/Leaping or swimming while carrying gear.

Jumping & Leaping
Characters can jump with a Very Hard Difficulty if carrying their Max Carrying Weight. That Difficulty is reduced by 5% for every Weight level they go down from there (Table 7-26 pg248). Moreover, the Difficulty is increased by 5% for every Weight level they go up from there.

Swimming
Per RAW, if the character is wearing any kind of armor, Athletics Tests are Very Hard.

If the character is not wearing armor, but is carrying gear (which RAW leaves to GM discretion):
Characters can swim with a Very Hard Difficulty if carrying their Max Carrying Weight. That Difficulty is reduced by 5% for every Weight level they go down from there. Moreover, the Difficulty is increased by 5% for every Weight level they go up from there.

The penalties for wearing armor and carrying gear do not stack – the largest penalty between the two is what’s used. If a character with any negative modifier from wearing armor or carrying gear fails a swimming Athletics Test, he suffers 1 level of Fatigue.