Reset MCP Altitude

[Paul12 2]

When doing an autoflight ( PMDG-737 ) I get message RESET MCP ALTITUDE.

I do this but prior to landing ( about 10 nm before the rwy  ) I get the same message again !

Question: what should I do ? What is the reason for getting this second message. ?

Usually I just ignore the message and the landing is ok.

But to me it does not feel right ! 

Thank you

Paul 12

[MarkJHarris 128]

That message comes up if the calculated VNAV descent is approached and MCP hasn't been reset to a lower altitude. The aircraft is calculating an idle thrust glide at ECON speed from cruise into a slow down at 10,000ft and another approaching the Centre fix for the approach selected. A continuous descent approach. 

Anytime you are reaching a constraint and a lower level is not selected on the MCP, the message appears to prompt you. 

Hope that helps.