Sample / draft. This note is not a case study and it does not name a facility.
What the drawing shows
A block-redundant scheme draws the critical load as several active blocks plus one reserve block. In normal operation the reserve block sits idle. If one active block loses its source, that block's load moves to the reserve. A second block failing at the same time is outside that design basis.
What a spare inside the block is
N+1 inside a block, such as three UPS modules with two needed, is a spare component. It is not a second path off the site.
Where to check the numbers
Read the capacity with the redundancy calculator, and read the drawing on the homepage as an illustration only.