Search console shows the position is 15.7 but in live even it's not in 100 positions.Why this is happening.
Try and filter by Country. Also switch off private search results if you're using Google yourself to search as this will bump up results that are more relevant to your user profile (which tracks location, search history, interests, etc.)
It will also show an average of all results, which includes bonuses/penalties from private results. If many local users lean toward using another site similar to yours, you'll find yourself bumped down in comparison for those users. Your average will appear lower. The same is true if many people favour your site - which bumps it up despite your actual rank appearing lower.
As Google has stated many times, there's no definitive ranking list. Each SERP is generated on the fly from many different metrics. Your 'rank' will appear in constant flux and will not be the same for all users.