How much memory matrix needs?

I am using matrix to change certain text in one of the worksheets. Matrix has size of 300 * 2 eg. it's code in VBA is

dim matrix(300,1)

Is there limit how long text there can be inside matrix?

How does matrix reserves memery space, does it take longest item inside of it, or does it allocate space according items lenght?

I aks this, because if matrix starts to take memery in meg's, then i must come with different solutioin.