what did my Dr mean 4-5 ahead?

My Dr did my Fundal height measurement thing and said I'm " measuring 4-5 ahead". I've been at the hospital all week with my oldest daughter having her new baby (my first beautiful grandbaby!!!!) with complications so it didn't register or occur to me to ask what that meant exactly - all I could think to ask was does this change things... He said no and we moved on. Now that I've had sleep I'm like, what does 4-5 ahead mean? Help me out please. My other pregnancies when they'd do that they'd say I'm 3 behind, consistent through the whole pregnancy with all my previous kids.