Help with range when buying

I want to buy a 40kwh N-Connecta Nissan leaf. Many cars for sale through Approved used Nissan here in the UK have different ranges shown in the sales pictures. I want advice on how to judge this:

Some cars show what appears to be a terrible range - for example 34 miles on 29% charge. If I do that Maths here, it would give me a range of only 117 miles! (34/29 x 100). the car in question only has 3246 miles on the clock. How can it possible only have a range capavity of 117 miles?

Others show a much better story if I do this calculation. For example this one in a jolly colour has 12614 miles and an apparent range of 123 miles / 83 percent = 148 miles, which is rather better.

https://usedcars.nissan.co.uk/en/vehicles/nissan/leaf/110kw-n-connecta-40kwh-5dr-auto-hkct7pz?referrerText=Nissan+LEAF+110kW+N+-+Connecta+40kWh+5dr+Auto&referrer=image_srp

Am I doing this calculation right? Is this a good way of comparing range on used approved Leafs? My method would suggest that the following has the best range of all:

https://usedcars.nissan.co.uk/en/vehicles/nissan/leaf/110kw-n-connecta-40kwh-5dr-auto-qxcx4zl?referrerText=Nissan+LEAF+110kW+N+-+Connecta+40kWh+5dr+Auto&referrer=image_srp

45/30 =153 miles.

Can you guys advise whether I am going about comparing possible purchases in the best way? Or is this range calculation method I am doing flawed?

Welcome. The range estimator on the Leaf (and on many EVs) is pretty terrible. On Gen I Leafs it essentially takes your driving efficiency from the last few minutes, applies it to the remaining charge, and gives an estimate that is usually useless. The Gen II Leaf Guess O Meter, as they are known, is better, but still can't be used in the way that you would like. Beyond looking at the number of capacity bars (the tiny bars at the ends of the charge or fuel bars on the dash meter for Gen I, and the separate battery-shaped icon on the Gen II) remaining, there is no way to tell the actual real world range of a Leaf from a photo of the dash. Your only option here is to assume that any car showing 12 capacity bars has just a little more than 85% capacity remaining, any Leaf showing 11 bars means just over 10 bars, etc. This is made more difficult by the bars on the Gen II capacity graphic not being delineated clearly. Fortunately, few Gen II Leafs have, at this point, lost more than one "bar" - or even one.
I'm going to link my used Leaf buying guide. It won't be perfectly accurate for UK and other European Leafs, and the part about 40kwh cars is smaller, but it will still help. http://www.mynissanleaf.com/viewtopic.php?p=538030

I look forward to the link -thanks for this. Am I right in saying the 40 Kwh doesn't have capacity bars ?

The bars are there, in the battery-shaped capacity gauge on one of the many display screens, but they aren't clearly delineated.

Do you mean the screen called battery capacity where there is a ruler like display with 12 segments, running from 0 to 1?

They may have changed it. I remember a AA-shaped battery icon, with no graduations.

https://mynissanleaf.com/viewtopic.php?p=608089#p608089 is what it looks like on gen 2 Leafs.

Apologies for remembering that graduated graph incorrectly. I was mentally confusing it with the temperature gauge. Thanks, Cwerdna.

No prob. https://www.youtube.com/watch?v=VfD1JvhC2zk at 1:10 also shows it.

Since OP is looking at used ones (missed that earlier), https://www.youtube.com/watch?v=ni7SKnw_Io0 at 1:15 shows the same thing.