Track and improve your reading speed over time.
Reading speed improves geometrically at first because the early gains come from removing subvocalisation and regression rather than from reading faster, so a weekly percentage compounds over a practice block. It does not compound forever: the projection is capped at 900 words a minute, above which comprehension of ordinary prose degrades sharply and what is happening is skimming rather than reading. The hours-saved figure converts the gain into the only benefit that matters — time recovered across a year's reading.
Projection
Projected wpm = current wpm x (1 + weekly gain)^weeks, capped at 900
Time saved
Hours saved = annual words / (current wpm x 60) - annual words / (projected wpm x 60)
Not as reading. Controlled studies find comprehension collapses beyond roughly 600 to 900 wpm because the eye cannot fixate fast enough. Above that you are sampling the page, which is a useful skill but a different one.
Reducing regression, widening the fixation span and building subject vocabulary. The last is the largest effect for academic reading — familiar material is read far faster than unfamiliar material at the same skill level.