Why can me do before race the tyre wear???

In Papy sims I can choose what tyres want to change in pit. In Lfs I must can know before start of race the tyre wear. When running test race the wear is xx.x % but on another race the wear will xx.x-1 % and the crew will not change my tyre and i will get a puncture before 2 laps of race end. Is it real??? On real life the racers instruct the crew before start on how many percents of wear will on race???

Ehh.