Algorithm to compute the shortest path in a weighted directed graph

I'm trying to solve a short paths practice problem and I've encountered this. I have no idea how to approach it, can anyone help me? A thorough guide would be appreciated, I'm having a hard time thinking about this.

Discuss an efficient algorithm to compute a shortest path from node s to node t in a weighted directed graph G such that the path is of minimum cardinality among all shortest s - t paths in G

In the initialization step, initialize the cardinality for all nodes except s to $\infty$. Set the cardinality of s to 0.
for each vertex v in vertices: distance[v] := inf cardinality[v] := inf predecessor[v] := null distance[s] := 0 cardinality[s] := 0
for i from 1 to size(vertices)-1: for each edge (u, v) with weight w in edges: dist_thru_this_edge := distance[u] + w card_thru_this_edge := cardinality[u] + 1 if (dist_thru_this_edge < distance[v]) or (dist_thru_this_edge = distance[v] and card_thru_this_edge < cardinality[v]): distance[v] := dist_thru_this_edge predecessor[v] := u cardinality[v] := card_thru_this_edge
Then, check for negative weight cycles (code is the same as shown in the Wikipedia article). If there are none, the length of the shortest path is distance[t], its cardinality is cardinality[t], and the path can be traced back from t to s using the predecessor array (i.e. the predecessor of t on the shortest path is predecessor[t], the predecessor of that node is predecessor[predecessor[t]], and so on). Remember that predecessor[s] is null and this is not true for any other node once the shortest path has been found.