I had a guy tell me last year he was fishing 150 back, went with him to the lake and that's about all the line he had on the reels, might have actually been 70 foot back. Its all relative, spool em the same and you have your reference, spool em full and you will be in line with the charts, remember too that line out starts where it enters the water too, I have my rod tips down on the water but if you have them up then the count would start where the line enters the water, say 70 feet off the reel but doesn't enter the water for 20 feet then its really 50 foot out as you are comparing to the charts.
Good luck and have fun, seems like rocket science but its not, more common sense than anything else.