it's funny -- i had the same misconception when i first joined, as well.
training is not day-to-day -- it is once a week. when the training counts is sometime on friday morning (east coast usa time) -- whatever you had directed the training to be AT THAT TIME is the "training" for the WEEK. You can flip and flop and waver throughout the week, switching to your heart's content, but what counts is that magic moment on Friday morning.
That said, the other important component is making sure your target trainees (with special exceptions) have played AT LEAST 48 minutes THAT WEEK. These minutes can be accrued during scrimmages, as well.
Let us run through a an example or two.
You begin the week torn between training rebounding for your center(s) or your jump shot for your shooting guard. You play three games that week. Thursday evening, you review your minutes played per position. You see you have your starting center with 72 minutes, a backup center you played during the scrimmage with 60 minutes, and an old fart who filled in with 22 minutes. Your review your shooting guards, and see your starter had 48 minutes, his sub had 48 minutes, and you were able to play a promising 18 year old in the scrimmage for 48 minutes. You need to make a choice -- you can train Rebounding (and two players will benefit) or Jump Shot (and three players will benefit). That is your choice for the week.
Once you catch on to the principles, and read the instruction manual carefully, and look at all the options offered on training and try to understand each -- you are ready to train. When combined with other facets of the game, it becomes almost infinitely complex. At a certain point, you will need a plan.
Good luck.