Why are some leads restricted to a user?

Hi all,

My colleague used to see all the leads, and suddenly she can only see the leadse that she created.
Somehow, her document now shows the restrictions as on this picture:

As from our knowledge, the only thing that we did was importing new leads with an excel file but we did not do any setting changes.

Can you let me know how to get rid of these restrictions?

Thank you

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