Where is this history log you mention? I only see one daily line showing something like: "Swap Payment on wallet deposit". All swaps done are put into one line of payment. Even though i did many different swaps for different percents.
From that initial history page, there's a row of tabs to view your history in different currencies and in more detail. The "Margin Swaps" and "Unused swaps" tabs hold your lending history. That said, it doesn't break down the payment amount any further - just lists the Start/End time, amount and rate.
Would be nice if it
did break it down to a per-swap figure, but if you're worried about the payments being a bit underweight, I can (sort of) vouch for their accuracy, in that I have a long-running spreadsheet calculating the expected return (amount * rate * duration * 85%) for each swap and hence my expected return each day. Going by that, I'm fairly sure they're not cutting off any part-hours or part-days.
It's rare that I'm wrong by more than a few cents, that's very plausibly because I tend to copy the times from when the notification emails are received (which is generally a few seconds later than the real start/end time), and the total accumulated error for the whole year is about $4... and in my favour, at that.
Yes, i think the returns are correct and pretty stable once you see it as per hour.
And yes, it would be good having a own line of payment for each swap. Of course that might get big fast but its the same for every trade. So i wonder why its handled differently here. Its not a problem of course.