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Receiving notification meaning 'receiving the message in system that says the 'Ontario government is interested in considering me for nomination under its Provincial Nominee Program (PNP) through Express Entry.'?

Say I receive this message yesterday, I will have to upload all docs and submit an application within 14 days?

No. you have 6 months to do that. The 14days deadline counts from when you create your profile on the e-filling portal for uploading your documents.
 
start uploading the documents mentioned in the ontario PNP guide .You have 14 days to submit the application

Not true! You have 14 days since the day you start to fill your application. Since you receive the NOI you have 6 months to accept it (Create One-key and fill the application).
 
Please stop giving fake information...