How to reproduce:
1. Open attached project "case_1162074-MaxOrthoSize.zip" and scene "SampleScene"
2. In Hierarchy window, select "CM vcam1"
3. In Inspector window, observe "Maximum Ortho Size" value (its '5' in my example)
4. In Hierarchy window, select "Main Camera"
5. In Inspector window, observe "Camera" -> "Size"

Expected result: the size value is 5
Actual result: the size is 2.5, half of the "Maximum Ortho Size"

Reproducible with: 2018.3.0b1 (2.2.8), 2018.3.14f1 (2.2.9), 2018.4.2f1 (2.2.9), 2019.3.0a6 (2.3.3, 2.3.4)
Not reproducible with: 2018.3.0b1 (2.1.13, 2.2.0, 2.2.7)
Could not test with: 2018.3.0b1 (2.1.12) and older due to package manager errors