T5, in a GrowLab, with maximum foot-candles, and digital light meter problems.

So here it is: I am new to growing and been having my fair share of problems. I have done the research; books, magazines, internet, etc., but yet still not having the best of luck. I am using a Sunleaves Pioneer VIII. It contains eight, four-foot VitaLUME PLUS T5 grow tubes(54w/6,500k). The T5 is suspended inside of a GrowLab 80L. The GrowLab's dimensions are: 2'7"x4'11"x6"7". I have a flat, placed on the floor, 7" humidity dome, with rapid rooters as my growing medium. The top of the humidity dome is placed 40 inches below the T5; and it is 47 inches from the light to the top of the rapid rooters.
Does this amount of distance between light and medium sound normal? According to the book MH, by Jorge Cervantes, seedlings only take a maximum of 375 foot-candles, or 4000 Lux. Before purchasing an open box digital foot-candle meter, I had the tray so close that it was registering 19.0 on the meter. After finding this out, I adjusted it down between 3.8 and 4.4. Since it did not come with manual, I am hoping the formula I used to calculate foot-candles is correct. I am using a Sunleaves Sungauge. It measures up to 5,000 foot candles. I have the setting to read between 2,000-5000. I took the number the meter reads out, and multiplied it by 100. Did I calculate that right? Important to note: Instead of using all eight bulbs, I had to shut off the outside four bulbs to get my light levels down. Also, I borrowed a friends Hydrofarm meter, and did a spot by spot comparison, and consistently was off by one whole number(100 foot-candles) Is there a way, through calibration or some other method, to decide which meter is off? 100 foot-candles represents almost a 1/4 of my light output.., yikes. Is there a certain recommended light meter brand I should invest in? Any and all information or suggestions is extremely appreciated. Thanks in advance.

CC, that's a thread-full...!

Just use 1 bulb @ appx 18" above the plant tops, regardless of the dome top. Wouldn't even recom the dome as you will likely have mold/damping off/crown rot issues, but that's me. Likely you won't use all 8 bulbs as I never have... they get hot & no real way to vent as with hoods. This will be plenty to root.

Pretty much the light meters in the range you mentioned are inaccurate at best. Have to invest in a relatively nice meter to have better calibration/sensitivity. Those will give you a ball park, but that's it. Quite frankly, it's overkill & you needn't be worrying on that. Such a thing will be the last of your concerns (or anyone's just starting).

Don't know what your temps are inside the humidome, but should check that & keep in the 75-78 range, if poss... no higher than 80. Hope this helps, best brah.

LOL--forget all that stuff and get that light closer to your plants. If these are established seedlings, get rid of the humidity dome and get some air circulating in there. I keep my T5 within inches of seedlings with no problems.

BTW, had it in my head you were taking cuttings... maybe i just saw humidome & made some leaps. Sorry if post wasn't directly related. Best brother!