Single vs double node style
Due to the complementary nature of DNA, assembly graph nodes actually come in pairs where their sequences are reverse complements of each other. Bandage names nodes ending with either '+' or '-', so for example, node 5+ is the reverse complement of 5- and vice-versa. Note that depending on the assembler, a node being 'positive' or 'negative' may have no real meaning – it can be random which node in a pair is positive vs negative. See the page Assembler differences for more information.
Bandage can draw and display graphs in 'double' style, where the two nodes in a pair are drawn separately. Alternatively, it can display graphs in 'single' mode (the default), where the two nodes in a pair are drawn together as a single node.
Here is the same graph in single and double mode:
Graphs drawn in single mode are visually simpler. They have half the number of displayed nodes and edges, which results in a less cluttered appearance.