。
There's just enough time to make the train.
Literal
Train [to-に] sufficiently in-time [only-だけ-の] time [subject-が] exists.
~だけの ('just enough to, only as much as') is a limiting-modifier pattern: quantity/extent marked as being sufficient for X. 十分間に合う ('be sufficiently in time') + だけの時間 = 'enough time to comfortably make it.' 十分 here is じゅうぶん ('sufficient'), the adverbial reading — pinned by the semantic role.