A Notice To Comply IS a warning, it is not a fine, although it carries the potential of a fine if you ignore it and the matter is taken to the Tribunal. A warning that you will be issued with an NTC is a warning that you will get a warning.
Also the building manager can’t issue NTCs – only the strata manager or strata committee can do so, and only then after having discussed the issue at a properly constituted meeting.
Also, the NTC has to include a copy of the relevant by-law that you are alleged to have breached.
So my response to the building manager (if it is them and not the strata manager) would be to ask if they are actually empowered to issue an NTC.
If you have confused the building manager with the strata manager, then tell them that you will be interested to see the NTC to establish which by-law they allege you are breaching.
If you do have an NTC issued, you could just ignore it until such times as you are summoned to the Tribunal (in six to nine months) and argue your case.
If the Tribunal Members feels you have breached a by-law, they will probably tell you not to do it again or the next time you will be fined.
Or they might say that for health and cultural reasons, many people leave their shoes outside their homes and a blanket ban is unreasonable. Or that it’s just too trivial a matter to even deal with.
However, as a tenant you are a little more vulnerable as a breach of by-laws may be considered a breach of your rental agreement. I would check that out but I can’t see anyone being evicted for leaving their shoes outside their door.
Finally, there are many requests elsewhere on this site not to post in multiple places on the same topic and with the same text. I have deleted your other post.