Pandas nunique() and value_counts()

Question

I'm doing a udemy course about Pandas, one exercise asks you to select the number of jobs mentioned once in the dataframe in the year 2013 (the dataframe contains employeename , year , salaries , job title , etc.. ) I used

sal[sal["Year"]==2013]["JobTitle"].nunique(dropna="True")

the output was 1051 the solution used value_counts()==1

sum(sal[sal['Year']==2013]['JobTitle'].value_counts() == 1)

the output is 202 If I got the basics right, I think the sum value_counts()==1 is the same as unique but I got different outputs any help please and thanks!

sal[sal["Year"]==2013]["JobTitle"].nunique(dropna="True")