I looked into this and it was just a display bug. I set it to PERCENT because the suffix can be selected with incorporating from the standard, but it displays 1/100 value because the value recorded is not the unit for normal percentage display to be used.
We can choose not to display "%" on the chart, or increment to the new save version and multiply by 100 when loading from the old save. In the latter case, the value read from dat needs to be multiplied by 100, or the value of dat needs to be multiplied by 100, so the former is easy.
const uint8 citylist_frame_t::hist_type_type[karte_t::MAX_WORLD_COST] =
{
STANDARD,
STANDARD,
STANDARD,
STANDARD,
STANDARD,
STANDARD,
STANDARD,
STANDARD,
PERCENT,
STANDARD,
PERCENT,
STANDARD,
PERCENT,
STANDARD,
STANDARD
};
In the former case, just change the end to STANDARD as above.