How to read your Oyster Card journey history

So as luck has it, I've answered myself while writing this post (one of the many advantages of writing I imagine) - I've left all the writing though because I want you to see what I meant. Post starts from here...

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Does anyone know how to read the oyster card journey history? I'm not having much luck. Am I being thick? I'm trying to figure out how much a return journey from Gospel Oak to Kew Gardens costs using London Overground. 8.51 am I touch through Gospel Oak's barriers. I'm assuming "-" means no fare as it's only entry and not a complete journey, and that 6.50 is my balance. I can't think what the -1.30 is for. 9.29 am I touch out of Kew Garden's barriers. 5.10 is clearly not the fare, however I can imagine my balance going from 6.50 to 5.10? But apparently my balance is 3.80 - did the journey cost 2.70? I have an incredibly blurry memory of seeing 2.** flash on the barrier. 12.03 pm I touch through Kew Garden's barriers. Again, "-" no fare, but is that my balance that's 4.40? You can see that there's actually quite a few 4.40's when I touch through a barrier - perhaps that's how much I'm charged if I don't touch out? And if that's the case, why is it different when I touch through at Gospel Oak (6.50)? My balance is then stated as -0.60, again this amount is a bit baffling. 12.45 pm Touch out of Gospel Oak's barriers. 3.10 OH MY GOD I'VE WORKED IT OUT How to read your oyster journey history... When you touch in through a barrier, you are automatically charged quite a large fare (it will change depending on where you are by the looks of it), so you can see where it says "Gospel Oak, Entry", I have been charged 6.50 which leaves me with a negative balance of -1.30 (if I don't touch out then I think this is what I'm left with). This means my balance before the journey was 5.20. When you touch out at your destination you are reimbursed (the amount you were just charged for touching through MINUS the actual journey fare) - so 6.50-5.10 means that Gospel Oak to Kew Gardens cost me 1.40. I then touch in through Kew Gardens using a balance of 3.80 (5.20 - 1.40), the system assumes I'm not going to touch out so it charges me 4.40, leaving me with a negative balance of -0.60. I touch out of Gospel Oak and I'm reimbursed 3.10, leaving me with 2.50. Gospel Oak to Kew Gardens on the London Overground costs 2.70. Thank you, thank you very much.