Please include the entire error message. It is easy to do. There is a button (lower right of the IDE window) called "copy error message". Copy the error and paste into a post in code tags. Paraphrasing the error message leaves out important information.
Arduino: 1.8.13 (Windows 10), Board: "Arduino Uno"
C:\Users\elopez28\Documents\Arduino\sketch_attinyOLEDtimer\sketch_attinyOLEDtimer.ino: In function 'void setup()':
sketch_attinyOLEDtimer:25:16: error: 'FONT6X8P' was not declared in this scope
oled.setFont(FONT6X8P);
^~~~~~~~
C:\Users\elopez28\Documents\Arduino\sketch_attinyOLEDtimer\sketch_attinyOLEDtimer.ino:25:16: note: suggested alternative: 'FONT6X8'
oled.setFont(FONT6X8P);
^~~~~~~~
FONT6X8
C:\Users\elopez28\Documents\Arduino\sketch_attinyOLEDtimer\sketch_attinyOLEDtimer.ino: In function 'void updateDisplay()':
sketch_attinyOLEDtimer:102:20: error: 'FONT6X8P' was not declared in this scope
oled.setFont(FONT6X8P);
^~~~~~~~
C:\Users\elopez28\Documents\Arduino\sketch_attinyOLEDtimer\sketch_attinyOLEDtimer.ino:102:20: note: suggested alternative: 'FONT6X8'
oled.setFont(FONT6X8P);
^~~~~~~~
FONT6X8
sketch_attinyOLEDtimer:125:17: error: 'FONT6X8P' was not declared in this scope
oled.setFont(FONT6X8P);
^~~~~~~~
C:\Users\elopez28\Documents\Arduino\sketch_attinyOLEDtimer\sketch_attinyOLEDtimer.ino:125:17: note: suggested alternative: 'FONT6X8'
oled.setFont(FONT6X8P);
^~~~~~~~
FONT6X8
sketch_attinyOLEDtimer:128:17: error: 'FONT8X16P' was not declared in this scope
oled.setFont(FONT8X16P);
^~~~~~~~~
C:\Users\elopez28\Documents\Arduino\sketch_attinyOLEDtimer\sketch_attinyOLEDtimer.ino:128:17: note: suggested alternative: 'FONT8X16'
oled.setFont(FONT8X16P);
^~~~~~~~~
FONT8X16
exit status 1
'FONT6X8P' was not declared in this scope
This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.