Strange hexadecimal comment at the end of a const in documentation

1. Create a new crate.
2. Put for instance const HOUR_IN_SECONDS: u64 = 60 * 60; into src/main.rs.
3. cargo doc --open.
4. Navigate to the constant.
5. See pub(crate) const HOUR_IN_SECONDS: u64 = 60 * 60; // 0x0_000_000_000_000_e10u64.

There is a long and very hard to read commented hexadecimal number at the end, 3600 in decimal. Why is it there and how is it useful to the documentation reader? Shouldn't it at least be in decimal?
Is this perhaps a bug?

I also can't find any documentation or sources on this behavior like in https://doc.rust-lang.org/rustdoc/.

@rustbot label A-rustdoc