Caller ID display 2 or 3 digit number

[ShinKen]

Over the past couple of days I have been getting calls where the caller id is only displaying 2 or 3 numbers

16
03
60
56
152
02
172
193
158

When I answer the call ends and goes back to the ooma dial-tone. Yesterday I recieved 5 calls like this and this morning I have recieved 2 already. Anyone else having this issue or know what is going on?

[DTMF]

Are these calls from unfamiliar callers, such as telemarketers? Telemarketers have been known to spoof their caller ID with unusual numbers in an effort to entice people who screen calls to answer sales calls.