The volunteer rota

The rota had been compiled from emails, telephone notes and sign-up forms. Two volunteers called Alex were identified only by their first name, so it was not clear which one had accepted the Saturday shift. One entry instructed a volunteer to arrive ‘after lunch’ without giving an exact time. The letters ‘WD’ and ‘RG’ appeared beside several names, but their meanings were not recorded. On Tuesday, the same volunteer was assigned to both entrances between 10.00 and 11.00. An email explaining that another volunteer was no longer available had been received, but the rota had not been amended.

Describe the difficulties of checking whether the volunteer rota was accurate. You may support your points with brief quotations.