Battery percent is pretty easy to understand.
what's the difference between the accuracy and accurate percent?
there seems to be large gap between the two.
Accuracy is basically how accurately the application is estimating your battery. So in the beginning, the app doesn't really have any data points to use, so your accuracy is low. As it collects more data points regarding your usage, the app gets more and more accurate in its estimation of your remaining battery.
Accurate percent is basically what the app thinks is your battery percent remaining. So with the droid, the OS reports the battery % left in 10% increments, so say it might say you have 80% left. But really you have somewhere between 70% and 80%. Your accurate percent is what Battery Left thinks your real % left is.