Anyone concerned about the low mileage of their marathon plans?

Used Runna for the Dublin Marathon last year. Overall, I was very happy with the plan (bar the frequently mentioned issues here about the intensity of the two speed workouts per week).

Currently working on a plan for my spring marathon and, despite going with Optimal and Advanced - the top mileage on the plan for the remaining 13 weeks is 52 which seems very low.

Anyone had similar issues or workarounds?