Inspecting behaviour of `make-overlay', is this expected?

[Jean Louis]

XXXXXXXXXX
^
| position 0 in buffer

(setq my-overlay (make-overlay 0 10))
(get-buffer-window (overlay-buffer my-overlay))
(overlay-put my-overlay 'display "Hello") then I get:

HelloX 

instead of "Hello"

Is this normal behavior?

--
Jean

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