Core: Under-signs: explanation, restriction, exemption and distance

Under-signs do not exist independently: the law opens with 'under-signs placed under traffic signs' — without the main sign above it, an under-sign has no meaning. What exactly the under-sign does depends on the precise text and symbol. If only a symbol appears (no text), that RESTRICTS the main sign to the indicated group or behaviour — for example a truck silhouette restricting a ban to trucks only. If the word 'uitgezonderd' (excepted) appears with a symbol, it flips around: that group is instead EXEMPTED from the ban — the opposite mechanism, with almost the same layout. At E-parking signs (E4 through E8, E12, E13) with days or hours on the under-sign, the order or prohibition applies only within that time window — outside those hours, parking or stopping is simply allowed. The book shows a concrete example: 'Monday through Friday from 8 to 18 hours and Saturday and Sunday from 6 to 24 hours' (Book p.252). For distance under-signs the book consistently uses 500 metres, in two different applications: '500 m' without arrows means 'applies over 500 metres from here', while '↑500 m↑' with arrows on both sides means 'applies for the coming 500 metres' — subtly different wording for two slightly different situations, but the same book figure: 500, never 600.