Close,
Look at what you are doing in the first loop. You are resetting this value to 0 at each iteration.
Does this will help
function nestedsum1(t)
total = 0.0
for i in t
#i is now a list in t
for j in i
#j is now an item in i (remember i is a list in t)
total = total + j
end
end
println(total)
end