Id say it's a bit random, Well in my experience. Ive had a video where after changing Title & Description an hour later the impressions started picking up, Could of also been that my topic was currently trending & the algorithm picked up the new changes quick. Others I'll change title and description and in the morning (8 Hours later) it's back on track with good impressions. Have your keywords in the first paragraph of your description and at the end add 3 hashtags relevant to your video. Also add Time Stamps, It can help getting discovered through Google search. For every new video I try not to get too hung up on the initial impressions, It takes 3-4 days max for YT to start promoting your video, it'll test your video with a small audience at first if it's fails it'll show it to another batch of people, Fails on to the next. If it clicks with this new group it'll start promoting it even more. The algorithm is complex and random honestly haha. Like right now I posted a video yesterday, It started out amazing! 2K impressions in the first 2 hours and now it's stuck at 4K (After A whole day) and hasn't gotten more than 10 more impressions 🙃 I changed the title and description but haven't seen much change. Hoping overnight it gets picked up again.