Pyramids yes, 0’s no
Ancient Egypt’s mathematical system did not have a “0”. 0 didn’t really solidify its place in mathematics until the 5th century (see here)
This may seem a small issue until we consider the tremendous value of a placeholder in counting. To convey 4988 in Arabic numerals you need only 4 characters, and it takes but a split second to decipher the meaning of this number. Compare to Roman numerals, where “4988” is conveyed MMMCMLXXXVIII. That’s 13 characters!!! (and most of us can’t look at that jumble of letters and immediately recognize it for what it means).
In a mathematical system without a 0, large numbers are incredibly unwieldy. When ancient authors speak of something “without number”, in cultural context they are speaking not of infinity in the strictest mathematical sense, but pointing out that they have no efficient mathematical way to describe it.
How to trigger your Computer Science teacher
Even today with computers we run into large number problems. Some computer languages are only designed to handle integers up to 2^32; this doesn’t mean there’s no such larger number; it just means the computer hasn’t been told how to process it. So naturally, as a computer science student, I plugged in a bigger number to see what happened….
One of the most common means of conveying an idea that is difficult to describe is via metaphor. The Bible uses metaphors a number of times to describe really large numbers (as the sands of the sea or as the stars of the heaven are some popular examples), including in the passage cited in the OP. This isn’t a mathematically precise statement, it’s an acknowledgement that it is a really big number.
We’re not all that different today; we use metaphors when something is difficult to describe. Think of all the metaphors used in love notes. Does anybody really intend to call their significant other a sticky substance made by insects? (honey)
They didn’t have a good way to mathematically reckon the amount of grain that had been gathered. In that sense it was without measure, and the most practical way to describe it was via metaphor.