Usually it means "Flashing" - so you should check if the numbers "04 26" are flashing on and off on the display. Usually, those flashing numbers denote special steps in the user interface of the software, like special entries that you should enter, or special variables that are displayed and should be noted on the PAD before continuing to the next.
For example the following:
V25 N07E
F 21 07 SET REFSMFLG
77E,10000E, 1E, V01 N01E,77E Confirm Bit 13 Is Set(Set If 1st Digit Is 1,3,5 or 7)
It tells you, that you should first enter Verb 25 ("Please perform (step in checklist)") and Noun 07 and press enter.
The next line tells you the expected response of the AGC: Verb 21 and Noun 07 should be flashing (07 = "Set REFSMAT flag" in the context of the current AGC program)
If this is correct, you enter the following inputs: 77 in R1 (The address to be changed), Enter, 10000 in R2 (the new value), Enter, 1 in R3 (set), Enter. Then Verb 01 ("Display in octal"), Enter, Noun 01 ("in R1"), Enter, 77 (from address 77), Enter. And confirm what the first digit of the displayed variable contains.