What do I input in the 'Property Value' box on shared ownership house?

What do I input in the 'Property Value' box on shared ownership house?
Added (1). Mortgage "property value" on a £180,000 house when I'm only buying a £45,000 (25%) share of a shared ownership house. Do I put £180,000 or £45,000 in the property value box.

As I'll be paying rent on the bit I do not own anyway which is 75%, so surely that's nothing to do with the mortgage company?

Thanks.

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