Well... I'm just slightly chagrined to say I don't know what "packing" is. But since you asked what it means having done it for the first time, I would venture to say it doesn't necessarily mean anything in terms of your gender identity. Perhaps it suggests you may be somewhere on the transgender spectrum. But it could also simply mean packing is something you learned about in some way or another and so you decided to try it out of curiosity. After all... we all have both feminine as well as masculine aspects to our personalities. And many, if not most, people I suspect have wondered at one time or another in their lives what it would be like to be differently gendered. That doesn't necessarily make them some variety of transgender (in my opinion.)

Perhaps I'm not telling you anything you don't already know. But determining your gender identity (when it's in question) can be a complex process that includes therapy with a skilled gender therapist, trying out different things related to your (potential) target gender for example dressing in the clothing of your target gender and (perhaps) cutting your hair as well as other things that make you look & feel more (in your case) male. It might even include some real-life experience; in other words going out in public presenting as your target gender (if-and-when you're ready for that.) It might also include joining one or more transgender forum websites and corresponding with others who have tread a similar path.

For those of us who question our gender identities reaching a conclusion as to our own individual gender identity can take time and effort. One single thing done, such as packing in your case, doesn't necessarily mean anything. At least that is my personal opinion. (Perhaps other PC members will yet have other thoughts on the subject they'll wish to share.) So you said you packed for the first time and you don't know how you feel about it. Assuming I'm understanding the point of your post (perhaps I'm not?) I would suggest what the experience you describe means is you have some additional work to do before you're going to know (to a reasonable degree of certainty) whether or not you may be some variety of transgender. I myself have been dealing with these sorts of experiences for decades. And I still haven't come to a really firm conclusion.