Bias setting

Recheck your amp’s bias after it’s been playing music, for an hour or two.      Don’t have anything playing, while you’re taking the measurements, just to be certain (but- stay within it’s nine minute window).      Check again after a week or so.    Then, a month.     Tubes take awhile to reach their potential best.      Slight deviations in your measurements, shouldn’t be a cause for concern, as long as you’re remaining balanced (between tubes).