Answer: No, the salesperson is not telling you the truth.
Step-by-step explanation:
Reasons are;
1) The exact number of pictures a phone of (X) memory cannot be determined due to the fact that pictures have carrying qualities and consequently would occupy varrying amount of space.
2) 10,000 pictures may or may not be stored in a 8gb memory phone, only an estimate can be given as the phone camera does not have the capacity to compress pictures to exact file sizes.