What it is doing on a modern title
Tithes were a payment in kind to support the parish, converted into money rentcharges in the nineteenth century and then progressively extinguished through the twentieth. What survives on titles today is usually a reference rather than a live obligation, and in many cases nobody has collected anything for generations.
It is also genuinely different from an estate rentcharge: there is no service being provided and no estate being maintained. It is a historical residue.