B.C. means 'before Christ.' So if something happend 1 year before Christ, that's 1 B.C. If something happened 10 years before that, or 10 years earlier, that's 11 B.C. The further in time you go before Christ's birth, or the earlier in time you go, the bigger the number gets.

I have read that BC originally ments "Before Caeser" and during the Christian reformation of Rome, it was changed to "Before Christ"

You are right, it is quite confusing. Actually, it is a negative scale, like for temperature Celsius. Bigger absolute negative values correspond to smaller numbers. Alternatively, you could consider to count the years for a particular environment from the begining of its existence. The Hebrew calendar counted from the date of the creation of the world according to the Bible, for instance. "Remember in history class when studying ancient civilizations you would get confused because some fellow would be getting older as the years became “younger.” For example, Caesar Augustus was born in 64 BC and 37 years later became emperor in 27 BC? How did he do that? Reverse time travel? This reverse time problem is also endemic to anthropology, geology, paleontology, cosmology and all the other studies that look back through time. Time moves forward, not backwards. AllTime eliminates this backward thinking and moves time forward, instead. The years advance as people grow older, and this follows the natural progression. Scientists call this "The Arrow of Time." There is no BC, no Years Ago, and no Before Present. It is so much more precise to say, "The universe is 13.7 Billion years old," rather than, "The universe began 13.7 Billion years ago." The first statement includes the age of the universe and the time that has elapsed since the beginning of the universe. The second statement expresses the length of time, but confuses the direction of time. No one who told you they were born fifty years ago would imagine that you might think they were now zero years old. The "years ago" statement is meant to be interpreted as moving both ways - you were born fifty years ago and you are fifty years old. The years ago system actually wants you to believe that the universe began 13.7 billion years ago and that it is now zero. This is counter-intuitive. Another conundrum created by Years Ago and BC is the "march-forward-to-fall-back" effect. Although the year number is annually reduced by one, i.e. 45 BC is followed by 44 BC, the year itself is additive. Therefore, it takes about 365 days starting with day one to add up to a year - only to lose a year. If that system were to be consistent, it might count days and months backwards too: i.e., December 31 would be followed by December 30. How to Get Time Moving Forward AllTime incorporates the entire expanse of time, not just a couple of miniscule millennia. It infuses all 13.7 billion years into present-day consciousness, not just 2004 years." Source and further information: http://www.alltime.info/reversing.htm

Because you are counting back from an event that is used as the base zero. If you were using a different base, such as the Hebrew calendar, or the Mayan calendar, the numbers would be quite different. Non Christians like to say "Before Common era" since that is more accurate than "before Christ".