Please clear up what exactly a partial fill up is.

[paulp5]

I have been using Fuelly for at least 24 years but the way I filled my car with fuel recently changed a bit which I will explain below. First of all I read the explanation in the FAQ section about partial fill ups but still need some more detail. I will tell you some actual situations that happened to me here.

Last year I drove my car on a long trip (18500 miles) partially off-road. I had fill ups almost every day and sometimes multiple times per day and I saved all my gas receipts and now I am catching up adding all these fill ups that I did not have time and many times internet to actually enter during the trip. With me I had 2 gas cans 5.3 gallons each which I filled at certain gas stations and later used at various times during the trip. My car fuel tank is 14.8 gallons. Sometimes I used the gas cans to fill my car because the fuel up ahead of my route was more expensive and sometimes because there were no gas stations nearby when I went off road. So I am confused about what a partial fill up really is. Several times I had a half a tank left in my car and pull up to a gas station and fill my car to full because the price was cheap, is this a partial fill up because I did not completely use the fuel in my car tank and added lets say 7 gallons. At other times I was driving to almost empty and I pull over and fill my car with the 2 gas cans I have which will only give me 10.6 gallons. Is this a partial also? Does Fuelly still calculate my average mpg over time even if I have a lot of partial fill ups or does it skip those? As I am adding all this data to Fuelly I am marking all fill ups which are below 13.5 gallons as partials because at this approximate time my car has roughly 2 gallons left and the fuel low warning pops up in the gauge cluster. Does in the entire history of all my fuel ups Fuelly knows all the fuel I ever added and all miles accumulated so It should give me a complete fuel up MPG value. Correct? I am not sure if the many partials I have are still calculated correctly in the complete history of all my fuel ups on this site.

Basically I want to know 2 things, what I wrote in the previous sentence and if I fuel up my car with gas to full but I only add 7 gallons is this a partial or a full fill up because there won't be as much distance added in that situation I see the mpg gets messed up whenever this happens. Thank you if you read all of this to the end.