It tells you whether you've attempted it before?
Mine went a bit batty toward the end. All the way through, upon landing, it'd say how many jumps are remaining - but on the last two jumps it just said "undefined", which had me worrying. One of three bugs I encountered over the weekend. The second saw my characters' stats change (Franklin's special skill was maxed out, but is now at about 65%. Not sure about all other stats.) The other had all three of my characters walking around with 1% health (flashing red), which wouldn't go up with snacks, health packs, visits to hospital, switching characters, or saving/reloading. Fortunately a reboot sorted it.
Hardest jumps for me on that powerpyx guide were 4, 12, 24, and 26.
Got them all in the end, though. I also did the knife flights (damn but one of those was a complete nightmare though!) and got my 100% completion badge.
I'm now going for golds in all missions.
Should be slightly easier than I thought. I did two of them last night, and it seems you don't need to fulfil all the criteria in your attempt - you just need to get the criteria that you didn't already have. So if you need to be fast and accurate and last time you were fast but had low accuracy you can just take your time when you revisit it.
I see you have two achievements I don't have, Kieron.
One required getting all three characters together, off mission, on a 3 star wanted level. I can't do that on my current game (need to restart or reload an earlier save. Tried a few early saves but none would let me get all three guys together).
The other appears to be for getting killed by a shark. Pffft - don't think I'll go for that one.
Online seems to be working much better now, btw, for anyone who gave up - and it's good fun. There's no heists yet, but there's still loads to do.
