A hiker's position is recorded as -20m (20m below base camp) and another hiker is at -5m

Why

Manav's reading of "20 is bigger than 5" is arithmetically true, and if these were both distances ABOVE base camp, he'd be completely right that the bigger number means higher up. The minus sign changes what the number means, though — here it's marking distance BELOW base camp, so a bigger number after the minus sign means going further down, not up. The hiker at -20m has descended 20 metres below camp; the one at -5m has only gone down 5 metres, staying much closer to camp level. As positions on a number line, -5 sits closer to zero than -20 does, and closer to zero here means higher up the slope. It's the exact same idea as money: owing ₹20 is a worse position than owing ₹5, and being 20m below camp is a lower position than being 5m below it. Aditi is right — the hiker at -5m is higher up, because with negative numbers, smaller distance-below-zero means closer to the top.