Hello @dahaiyu and welcome to the forum!
The dSPM and sLORETA algorithms produce source estimates in unit-less values (based on F-statistics).
On the other hand, the MNE and eLORETA algorithms return the electrical current in Ampere meters (that’s why the numbers are so tiny!).
It is therefore totally alright to label the y-axis in your above figure as “dSPM value”.
Hope that helps!
Richard