Usually a module mark is the overall mark, but nobody can say without knowing the rules for your uni.
Capped at 40 means you cannot get a mark more than 40 on the resit assessment, but it doesn't say anything about how the final mark for the module is calculated. If the final module mark is normally the average of the 2 assessment marks then it probably still will be. But if you have to get a pass for each component assessment then a 30 is no good. You need to look at how the module result is determined