Confused

Hey! So I did my 2nd Amazon flex today. Compared to my first route it was completely different, I actually really enjoyed it. But I’m just confused how the pay works? I know when it gives you a block it’s an estimate of the pay. However for my first delivery I booked a £57 3 hour slot, and due to a diversion and issues with the map I ended up finishing about 1-2 hours later. And they ended up paying me £5 less. Well today I also did a 3 hour slot for £57, I managed to get everything done on time and finished my last parcel 30 mins early. Obviously it doesn’t take into account the journey home, so technically by the time I got home it had been 3 hours. But they have said I’ll receive the full £57? So how come I had £5 deducted the previous time? Was it because I was running late?