Question

what the four figure grid reference of mountain 258 in 45D/7

Answer 1

When giving a four-figure grid reference, you should always give the easting’s number first and the northings number second, very much like when giving the reading of a graph in school, where you give the x coordinate first followed by the y.
An easy way to remember this is that to get the first number, you go along the corridor (horizontal, x axis, easting’s) and then up the stairs (vertical, y axis, northings).