To reproduce:
1. Create and open new project
2. Open build settings
3. Choose iOS build
4. Open Player settings
5. Write any integer number (for example 10) to "Target minimum iOS Version" field

Expected result: value 10 should change to 10.0
Actual result: value changes to default 7.0, but if you write 10.0, value is changed to 10.0

Reproduced on: 5.5.0b9, 5.5.0b10, 5.6.0a2;