Obviously Mhalir-4376 is not going to ignore it, even though it's, at the moment, pretty unclear what to do about it. He can afford to take some time and think about it, though.
What does it mean? Or, rather, what are the possible things it could mean, it's far from enough information to narrow down to a single world.
Either Andalites, or false alarms (not that unlikely, sensors throw false alarms regularly, though three of them is less likely...) Or - some third option, that he isn't seeing yet. Another species, with better technology, stepping into the war? Not impossible.
Improved shielding. This - isn't very surprising at all, both sides are improving their technology, it doesn't do much to decrease the likelihood that this is the Enemy.
Nothing spotted in space, though. That...makes it less likely to be Andalites, and more likely to be either false alarms or - unknown unknowns, the blind spot he can't even locate. It's not impossible an Andalite ship could have jumped here and slipped past the perimeter, but he's been on alert for that.
If it is the Enemy, then... Three shielded transits, in two weeks, in a remote state. No interference with any of his operations, at least not yet. Not an attack in force. They would absolutely be frontally attacking if they could, so...what does that mean... Limited resources, maybe. And a subtler Andalite mind in command than what he's seen before.
Mhalir-4376 thinks it through for some time, in bits and pieces in between other responsibilities and then in a longer block, with the lightning-quick ease of an Andalite's mind. (And tries, as always, not exactly to ignore Alloran's misery but to accept it as reality, not indicative of any error.)
Later that day he goes back to one of his lieutenants. <We have no presence on the ground in Alaska as of yet, correct?>