See an example below.
8.44 decimal hours = 8 hours and 26 mins, and 8.43 decimal hours = 8 hours and 26 mins. Since these are the same value, the system is rounding them to 8.43.
It's recommended to use values that are increments of 0.05 to avoid having rounding issues when creating work patterns. I was able to successfully create a work pattern of 37.5 hours by using 8.45 Mon-Wed, 8.40 Thurs and 3.75 Fri. I have attached a screenshot of this for reference.