What does delta stands for in ModelSIM?
A delta is a small (infinitesimal) time increment that is used during simulation.  The number listed is the number of these time steps that were taken to resolve the signal timing.  You can suppress these with the -NODELTA switch on the command line.

This is telling you that the signal is changing after the main time tick event.  To know what value is presented at the next time tick, you take the last delta value.  So for the 460 ns value you take the 460 +5 as the value out just prior to the 470 ns time tick.

If you want to know what activity was happening just after 460 ns then you look at the deltas.