That is why I stated it's implied. You have to look at the few ways they speak and talk. Very subtle a bit too subtle I caught on to this in the story because I use to do nothing but read books when I was younger.. I have read hundreds of novels good and bad and this is a decent story amateurish yes so too subtle.Was it months?
The way the scene played out, it made it look like it was his first sparing season with the other girl and was instantly powerful and in the later scene was full on badass against the aliens.
Even if the text was adjusted to it looking like it was months, it would still be kind of jarring.
At least two scenes would be good in the training, like one where he losses and another where he unlocks his powers to make a decent amount of sense.
It is hard to write like months gone by when you have daily events. You can either bore the user to death having them do 30 days of nothing or do events as day events. So the only possible way to even semi pull this off would of been in the writing of the event. You have not been back to the ship in about a month let's talk to everyone and see what has transpired.. Something to that effect is the ONLY way it could be done. Lines written out like this would of helped alot.. like to the effect of Our scouts after a couple of months has finally located the enemy now we have to plan for the attack. It will take us <insert time here> to reach the enemy make sure to get prepared for the oncoming battle.
Think Star Trek you watched a one hour episode but you had a sense of a lot of time had transpired.. Stupid things like the soonest we can get there is a week Kirk.. Make it 5 days Jim! Do you really think them stupid lines were said for no reason much of the time? It was to put in the sense of how long they been traveling so you got the sense of a week passing in a 1 hour episode.