Board Game Arena

The overall BGA average is about 80 and the winners are about 79.5

I am very sure it means the following:

The number gives a percentage value. If all your settlements and cities are bordering to 3 hex tiles you get a value of 100. If all your settlements and cities are bordering to only 1 hex tile you get a value of 33.3.

One example: You have 5 settlements in total. 2 settlements bordering 3 hex tiles, 2 settlements bordering 2 hex tiles and 1 settlement bordering 1 hex tile. In total you are bordering 3+3+2+2+1=11 hex tiles. Your optimum (100%) would be 5x3=15 hex tiles. Thus the value for "Average number of tiles around settlements and cities" is 11/15=73.3.

Please note that it makes no difference for the calculation if some or all of your settlements are cities. Cities do not count more in this statistic.

As the BGA average is 80 and the winners have an average of 79.5, one could interpret this fact as follows: The winners value the harbors (a tiny little bit) more than the average BGA player.

This statistical value is rather meaningless, however, since the average value mixes 3- and 4-player games and the number is very different for those. In 4-player games the value will always be lower since there is less space and all the players are forced to move to the shores...

Nice explanation. The slightly lower percentage for winners can also just be due to them having more settlements than the average player, given that usually the starting settlements are most likely to border on 3 hexes, while the new settlements from expanding are more likely to border only 1-2 hexes.