`tval.tv_usec` is a (signed) `long` and `ssPrec->m_offset` is an `unsigned int`. Clang warns upon realizing that we are attempting to divide a signed `long` with an `unsigned int`. Casting the `long` to `unsigned long` makes both operands `unsigned` and allows for auto conversion to `size_t`. The `size_t` cast is to make it apparent that the cast is correct.