Professionals ?

After getting the quotes from the insurance company there is errors in simple addition.
If quotes have these simple errors how can the rest of the quote be accurate? I am but a simple man with a simple education in engineering. Could you imagine me making a small mistake in building a bridge or a oil rig being as much as 10% errors against the the safety of the job.
How can a company a large company work with these errors and have credibility in the market place.
We are looking at the "y disasters" from the "y" generation.