Field 52630 is the spouse's net income after tax payer's entry date; 

Field 52670 is the spouse's net income before the taxpayer's entry date.

So the net income of the spouse  reported on her tax return is necessarily equal of the sum of these 2 amounts.

52630 is the spouses income before they emigrated to US

52670 is the spouses US income after they left.  

Is there an instruction page for emigrants? Obviously I have incorrectly entered something

for emigrant, you enter the date of departure, not the date of entry