Clarify documentation of nc-previews-auto command (#1370)

Author: thomasheller

etc/ncp-config.d/nc-previews-auto.cfg

@@ -3,7 +3,7 @@
   "name": "Nc-previews-auto",
   "title": "nc-previews-auto",
   "description": "Periodically generate previews for the gallery",
-  "info": "This will make browsing the gallery much more smooth.\nFor big collections, this can take a LONG time depending on your hardware.\nYou can specify a nightly duration in minutes, or 0",
+  "info": "This will make browsing the gallery much more smooth.\nWhen active, previews will be generated every night at 2am.\nFor big collections, this can take a LONG time depending on your hardware.\nYou can specify a maximum duration in minutes, or 0 for no limit.",
   "infotitle": "",
   "params": [
     {
@@ -14,7 +14,7 @@
     },
     {
       "id": "RUNTIME",
-      "name": "Runtime (in minutes)",
+      "name": "Max. runtime (in minutes)",
       "value": "0",
       "suggest": "0"
     }