No surprises in that oil analysis, first oil change interval was too long. I did not bother with an analysis for my 50 hour or the 100 hour change but I will send in a sample at 200 hours.
Check your owners manual maintenance interval, my L2800/3400 list oil and filter change at 50 hours and then 100 hours, then every 100 hours after that. The kubota website is a general guideline, I would follow the owners manual.
My first oil did not turn dark on the dipstick untill I had 30 some hours on it. The last oil change (100 hours) is getting dark after 20 hours but not black yet.