Sum Time Issue

Hi,

Can someone help with this file please?
The Sum doesn’t work properly

For the Average, I got some assistance by a member here
=((HOUR(b42)*60+MINUTE(b42))/COUNT(b1:b40))/1440

I believe this works just fine, however, if something wants to suggest something else, please
However the most important thing now how to solve the Sum issue

Hint, the whole reason behind what’s happening the nature of the generated report from where I get my data, as the timing with the date there comes like 1/1/1970 9:02:00 AM for instance, and there will be no possibility to change this

great
but there is a problem makes this formula doesn't work with me
that the range B1:B40 will get blank cells occasionally
like If I'll calculate the Sum for B1:B50 (10 empty cells there)
It'll not generate the needed results
I've tried sumif(b1:b50,<>"") but it doesn't work I don't know why

Well, I figured it out
I believe I need to use this
=SUMIF(B1:B50,"<>")-SUM(COUNT(B1:B50)*25569)

I believe this sort the blanks issue
Thank you so much
You helped me a lot