Facebook Promoted Ad Report Doesn't Tally With Shopify Report

[Isabelle-Allix]

My Facebook promoted ad is to get 'website visitors' for 7 days. At the end of the promoted ad, the total link clicks I received was 145. However when I check on Shopify under "Sessions by referrer" it only shows we have 88 visitors coming from Facebook. Are there ways to find out why they do not tally? And what is the reason the numbers do not tally?