edding markers should ideally be stored horizontally (e.g. lying flat in a drawer) and at room temperature. This way, the ink in the filter, which is located in the marker barrel, is distributed evenly and the marker writes cleanly until empty without residues drying out in the filter. Storing them this way means that the markers can be refilled when empty.
Storing the products incorrectly with the nib upwards could cause the ink to sink and settle and this means the marker won’t be ready for immediate use. You need to turn the pen so the nib faces downwards and wait until ink flows back into the nib.