Hello Pinwheel, My opinion about your large drill hole and the possible answer to its meaning is very possible thats its showing a distance and a direction, work it as you would any drill hole Width / depth, since you dont have the measurence's If you have a drill hole 4 inches deep ( 10 cm ) 4 inches wide ( 10 cm ) = 2 or two X circumfurence which is 34.5 cm = 69 which is a cordel, or 69 paces ( 33 inch pace ) = 189.5 feet I would use this for any drill hole anywhere, If its a 8 inch wide and 4 inches deep its 2 cordel, if it has a sholder 1/2 way down then its 3 cordel or 3 X 189.5 feet, the process is the same for any drill hole used for distance if its 16 inches wide then its 4, and if its 16 inches deep then the same principle applies. It may imply that its 7 cordel or 1/4 mile or 1326 feet, yours may be a league or 1/2 league which may indicale that you are on the property line of a league square an the long / short may indicate the magnetic directions or go both directions one distance is long one is short. I will add that a 3 inch drill hole may indicate measure by the foot,