I wouldn't worry about it- I don't think that it is overfilled enough to be a problem. I am not sure if the design of the ST1300 engine is such that the crankshaft can run through the engine oil if it is overfilled but this would probably be my only concern if it is possible. If you are concerned go out for a test ride at high rpm. Go from high rpm to a stop and check the oil in the sight glass right away after shutting the engine off. If the oil is all foamy air is being whipped in to it by the crankshaft acting like an egg beater. That is not good and you should drop the oil level. If all appears normal then I would say leave it alone until the next oil change. Checking the oil level using the procedure in the manual will yield varying sight glass oil levels. This is not a concern as long as the oil level is between the upper and lower lines. Don't let it bother you- just go ride. However, if you want consistent sight glass readings don't use the procedure in the manual. When I was new to the ST1300 I was told that the sight glass would always yield varying oil level readings because of the oil pan design. I have never believed this because it does not make sense to me. I set out to prove this to myself and I did so and I no longer experience this. Changes to the reading obtained through the site glass can only be due to changes in variables. The engine design is not one of these changeable variables. Even if there are baffles in the oil pan they are always there and they always restrict the same amount of oil as their placement and design does not change from one oil check to the next. If you check the oil level the way that the manual states to you will obtain varying readings. This is because there are several variables that are always different using this procedure such as the amount of time that you wait before performing the check, how much the engine has cooled off, how much the engine oil has cooled off, how much engine oil has drained back down in to the pan, etc.. All of these are variables that will influence the level of oil seen through the site glass. The very first time I checked the oil on my ST1300 I thought that the procedure in the manual was strange because of these variables. I was getting varying readings as well until I abandoned this procedure. Most every other engine I have ever owned the manual states that the preferred method of checking the engine oil is when the engine is cold- that is at ambient temperature- and before the engine has been started. The reason for this is to avoid the influence of these variables. If the bike is parked on a level surface on the centre stand and the engine, the coolant and the engine oil have all been allowed to completely cool to ambient temperatures then enough time has also elapsed to allow all of the oil that can drain back to the oil pan to do so. This method eliminates all of the variables except oil loss due to leaks and consumption. Under these conditions, assuming that there is no oil loss due to leaks or consumption, there is no reason that the oil level will not always be consistently the same when viewed through the sight glass. When I get home I park my bike on the centre stand. I will only check the oil level before I am about to start the engine the next time be that the next day or the next week. I am fortunate that I do not have any oil leaks and we all know that the ST1300 engine does not burn any oil so those variables currently have no influence either. By doing this all of the variables that can influence the oil level have returned to the same baseline state that they were in when I did the last check so there is no reason for the reading to vary. Using this method my engine oil is always consistently at the same level when viewed through the sight glass.
All the old eyes here will thank you!