When the maf'ul mutlaq is used only for emphasis, a synonymous verbal noun may also reinforce the action.
جَلَسْتُ قُعُودًا — I certainly sat down.
- the verb is جَلَسْتُ;
- قُعُودًا is a synonymous verbal noun meaning sitting;
- it is mansub and emphasizes the action.
Do not turn this into a rule for every use. When kind or number must be stated, the chosen expression must actually convey that information.