Yes, that is correct. But consider that the facility level raises with each update 2 steps. so:
1 Target Shot: 28 days
3 Junior Pitch: 24 days
5 Mini Camp: 20 days
7 Football school: 16 days (requires all other facilities at at least level 4)
...

It is like at the other facilities except stadium. At the stadium there you level with 1 upgrade level step each upgrade. So stadium is the bottleneck.