GDAX 64+bitcoin transactions

I've been watching GDAX for several months and I see repeating offers to sell 64 + bitcoins (not 65 or 63). This seems very strange as it's an unusually large quantity and is repeated several times a day. Can anyone make a quess as to why this would be happening?

After continous monitoring I've determined it's someone spoofing (attempting to drive the price lower). The bid always starts out $3-$5 out from the current price and as it gets close to the bid it's offer changed a few dollars higher but is never allowed to meet the current price. Interesting.....