So guys I ran my first FB ad campaign. Post page engagement ad. The estimated reach shown was 490 - 1800 during campaign set up. After the ad is completed, the paid reach shown on my post is 145 and reach shown in ads manager is 56. First of all, why are both these numbers different? Shouldn't they be the same? Secondly, there was zero engagement. Not even a single click, like, comment, nothing. The target audience was quite narrow and niche relevant. What could I be doing wrong?