What is the significance of V(0) = -j in finding position vector?

[Miike012]

Problem: Find position vector given
a(t) [ look in paint doc]
v(0) = i,
r(0) = j

I highlighted a portion in the paint doc that I have a question for. Why V(0) = -j + C? = i?
Where did they get the -j??

Thank you.

 

[Miike012]

Never mind I got it