When DC input, the SA should be damaged. If lucky, only the RF variable attenuator will be damaged, the result is if you input 0dBm signal, the SA will display about -30dBm. Because SA has several attenuators, each for different freq band, sometimes only one attenuator is damaged, others are good. So SA can't measure amplitude at some freq band, but at others freq bands, SA is good. The worse case is the mixer of the SA is damaged, so the noise floor is very high.
You tag means: the AC and RF signal Maximum input signal should be 30dBm.
I guess your SA has some functions like oscilloscope, so you can select AC coupled or DC coupled. When you selected DC coupled, should not input DC signal.
When you select AC coupled, the maximum DC voltage is 50V.
Because I never used the DC or AC coupled SA, I am not sure about that, the last two points meaning on your tag.
Hope someone else can help you. Good luck.